Lumen is a 5'3" pretty woman in her early 30s with long blonde hair, and a slender body. She has multiple scars on her back, caused by beatings suffered at the hands of the Barrel Girl Gang. In her initial appearance, she is dirty, and her clothing is ragged, a result of her confinement and abuse.
After Dexter rescues her, she often wears her hair back in a ponytail with light makeup, along with various sets of clothes which Dexter presumably rescued from the motel storage. This includes a hoodie used when she stalks Robert Brunner and later searches Alex Tilden's house with Dexter. Her kill uniform is a navy blue long-sleeved shirt, dark jeans, and gloves that Dexter gave to her.
To keep Dan Mendell from recognizing her, she wore a black wig and heavier makeup to mask her appearance.
When Dexter first finds her, she is quite fearful and thinks that Dexter is going to kill her just as he did Boyd Fowler. As she is very distrustful of Dexter, she puts up a fight and attempts to flee multiple times. She believes he may be a member of the group that tortured her..
Lumen eventually begins to trust Dexter after he confronts her with what would have happened to her had he not rescued her by taking her to the site where the barrels containing the previous victims of the group were dumped. She heals his wound and informs Dexter that there are more people like Boyd. She is shown to have fierce determination and she takes direct action to kill all the men who brutally raped and tortured her. She feels that she can't find peace until she knows they are dead.
The extent of this psychological damage can be seen whenever someone touches her or if she's confronted by multiple men, It reminds her of that time in her life when she was tortured and abused. This occurs during her attempted escape from Dexter when she refuses to get into the car with the male teenagers and again when she's being searched at an airport, with people watching her. On these occasions, her vision blurs and sounds are muffled, she assumes everyone is watching her with the intent of rape.
She appears to be very determined to free herself of this anxiety by killing each and every one of her former attackers. She is shown to be obsessive, but very intelligent in finding her attackers much like Frank Lundy tracked Trinity. This was proven when she disguised herself to track down the men from the bar she was abducted from and correctly tracked down Dan Mendell (though she didn't have all the proof from before, but to track him down correctly is still an impressive feat).
She demonstrates a strong sense of recollection based on all her senses, which she uses to track down the perpetrators of the rape and torture to which she was subjected. She tracks down Mendell based on feeling and the memory of the taste of his fingers in her mouth. Her recollection of Jordan Chase' voice saying "tick, tick, tick" leads her and Dexter to identify Chase as a member of the Group.
As the season progresses she becomes more relaxed in Dexter's company, in spite of knowing what Dexter is. She displays friendliness towards Dexter and his family, helping Dexter when Astor and her friend Olivia arrive from Orlando, babysitting Harrison when Astor and her friend go missing. Due to her experience of mistreatment from the group, Lumen has demonstrated compassion towards the sufferings of others who have been hurt like her, for example upon seeing Olivia's severe bruising, disclosing to Dexter that Olivia had been beaten.
Even though she is distrustful of Dexter after witnessing him kill Boyd and being held captive by him, Lumen eventually grows to trust and respect Dexter. After Dexter gives her a knife and allows her to lash out at him without reprisal, she realizes she can, in fact, trust him and then tends his wound. After Dexter gives her his name, she expresses her gratitude in a moment of awkwardness.Later, when she tracks down Dan Mendell on flimsy evidence, angering Dexter, she apologizes for putting him in that position. After hearing that she can't find peace 'till all of them are dead', Dexter wants to help her (due to the guilt he feels for Rita's murder) and takes it upon himself to aid her in her vendetta. Though there are times of tension between them due to Lumen's nervousness over Dexter's secret, she eventually comes to understand what it is he does after the death of Cole Harmon - Dexter confesses why he does what he does and thanks Lumen for helping him. to restore to him his sense of purpose. He even brings her along to help throw Cole's body into the ocean. Upon learning of Harmon's collection of DVD recordings of the Group's victims, she is angered by their callous reference to her merely as "thirteen", and she tearfully thanks Dexter, saying he is her "only way through this". After Dexter facilitates her killing of Alex Tilden and apparently moved emotionally by this catharsis and the connection they share, she and Dexter become intimate after returning to the apartment. For the first time in his life, Dexter feels that he has found someone who understands him for what he is and is not repulsed but is instead attracted to him. However, once Jordon Chase is killed, Lumen, having lost her Dark Passenger, states that she has to leave Dexter to move on with her life. Dexter is apparently sad that she won't stay, but is also happy for her that she reached a resolution of her inner darkness, something he feels is impossible for him. Lumen tearfully thanks Dexter for everything and promises she will tell no-one of his secret.
As a very important character, she gets her own featured style of music as well. It is a very gentle tone, having some of the instruments used in Native American tribes to most likely symbolize her abstract and difficult past, as well as her currently terrible life.
When Dexter Morgan begins his hunt on Boyd Fowler, he finds out that Boyd is a serial killer that murders young women and leaves them in drums out in a pond. After some complications, Dexter finally catches Boyd and begins the usual ritual to kill Boyd, but little does Dexter know that someone is watching him through a door with a glass window. After he claims Boyd's life, Dexter looks to spot a shadow in the glass and he quickly opens the door to find a shivering woman in ragged clothing. She collapses shortly thereafter trying to get away and reawakens in the Traveler Center that Dexter intended to be Boyd's kill room (though that did not go exactly as planned).
Dexter then takes her to a cabin, to keep her from escaping and telling of Boyd's murder. Much of her time here is spent avoiding Dexter, trying to escape him and even lashing at him, though as Dexter tries to figure out who she is, she tells him nothing and denies any medicine he offers. As Dexter leaves, however, she finds that she's ready to "obey" his requests and apparently takes the medicine, much to Dexter's surprise. Later on, as Dexter researches her and finds out that her name is Lumen Ann Pierce, along with the fact that she's from Minnesota. Dexter further delved into her information and found a room at the Towne House Motel she had rented out, containing the belongings she had leaving from her family to try and start a new life. Amongst these possessions was a letter that Dexter read but left for Pierce to read as well, whenever she decided to awaken.
Upon reading the letter, she bursts out in tears and continues to wait to escape this new type of prison, though only to keep her put until Dexter can figure out how to handle the situation. She comes up with a ploy, however, faking to have OD'd on the floor whenever Dexter returns, this tricks him and allows her to hit him over the head with an object, making her way for an escape through the woods (not before thinking fast and locking the door behind her with a padlock). Dexter's strength however prevails and allows him to burst through the door, chasing her on even footing the entire way until she makes it to a road where some teenagers in a car are passing through.
This is the first time we see Lumen's "vision" of the world and its dangers. Much like someone who has impaired vision because of alcohol, whenever confronted by something that poses a threat to her or might try to rape her, time slows and her vision begins to waver and move, the noise around her becoming muffled. The teenagers drive on and she keeps walking, only to be taken down by Dexter and held until he can get her safely into his vehicle.
The two make their way (with her arms zip-tied to the back of a seat) to where Boyd was keeping his dead victims in barrels so that Dexter can show Lumen just what fate would have awaited her provided Dexter hadn't saved her life. The entire time up until seeing the drums she's been very frightened, constantly trying to break free of Dexter's "enslavement" and especially now, as he brought her closer to them, she could feel a sense of dread coursing through her body. Whenever she sees the bodies, she can hardly control the shock that envelopes her, but Dexter goes on to lecture her and even gives her a knife, showing that he can be trusted...and he somewhat trusts her as well. Of course, she uses it to cut him but she ends up deciding to heal that wound, conversing with him some more. Much to Dexter's surprise, there was more than just Boyd who had her captive and tortured her, but more men, men she holds a deep hatred for.
The next time Lumen is seen is at a meeting place the two have decided on, where Dexter has bought her a plane ticket to leave Miami and head home to her family. Lumen, however, is filled with the desire to hunt down her assaulters, something Dexter constantly tries to tell her is a bad decision (most likely wanting to avoid her turning into someone he'd have to kill in the end). The two part ways for a bit and Dexter begins looking into Boyd's past, trying to find something that might link him to other associates, even returning to his house for clues. However, when he arrives, it is clear someone has broken in and was looking for something, frantically. Dexter finds blood, including a thumbprint and assumes it is the sloppy work of one of Boyd's helpers. As he researches the print, however (with Harrison's assistance), the print actually belonged to Lumen and this causes Dexter to worry further.
Dexter goes back to her motel room, knocking on the door to see if she was there but when no one answers, he just breaks his way in as usual. When he enters, a wall filled with sticky notes and obsessive research greets him, much like Agent Frank Lundy's Trinity research. Except this was for Lumen's attackers, to which she came up with a conclusion that Robert Brunner was one of her attackers. Dexter also notices that instead of sleeping on the bed, she used the closet, his observation is a way to keep her safe. Harry begins to question Dexter over and over if he should trust Pierce because of how she appears (a frantic, unstable woman who could be unpredictable and even make Dexter out if she is caught for murder), but Dexter mostly ignores him and confronts Pierce directly about this at their usual meeting place. Upon insisting yet again that she throw this behind and leave, him suddenly grasping her arm forces her to yell out not to touch her...which startles everyone around. This proves further that she is rather unstable since her capture by Boyd and his friends, suffering jitters and jumps at the slightest touch. The two once again part ways, with Dexter searching down Robert Brunner.
After finding Brunner and confronting him (to which he learns that Brunner is a rapist but also learns that he couldn't have done it due to an ankle bracelet that would track his location), Dexter tries to find her once more at her motel room only to hear from the caretaker that she's off to Tuttle Bridge, a location that Brunner lives and where many ex-cons spend their days. She enters the area wearing a dark gray hoodie and dark pants, hiding most of her features so at first everyone just assumes she's a skinny guy. However, when one guy bumps into her, he suddenly realizes she's a woman but she makes her way further quickly avoiding the fellow. Searching around the many dirt bags in the area, the fear and anxiety starts to return to her until she finally spots Brunner, her target. She keeps in the shadows as she follows after him, having a revolver on hand to take his life.
However, Dexter intervenes and after a brief struggle, he convinces her that she shouldn't try and take his life because he's not one of her attackers. After she becomes terrified at what she almost did, the two of them leave...later meeting up at an airport to bid each other farewell. Some chemistry begins to spark between the two and Dexter watches on as she thanks him and leaves...this kind of catching him off guard and he tosses in a "you're welcome" after about 10 seconds. When Dexter leaves, however, she tries to go through the detector and they require a full body search of her. Unfortunately, she is still under the same vision she felt earlier, except this time it takes over her senses (even though it's just a woman doing the search). She watches as man after man passes by, as the woman feels around her body for any type of weapon...and all the while she's taken back to that place where she suffered, she nearly suffers an anxiety attack but eventually the search ends...and it was too much for her, she's not ready to go on her own back to the home she left behind...she has to finish the problem here.
Next, she is seen getting into a taxi in Miami, thus revealing that she had never left at all and intends to continue her hunt.
As Dexter prepares himself for another kill, Lumen is on a hunt of her own for one of the men responsible for her rape and torture. Preparing herself in a full-blown disguise with a dark brown wig, spaghetti strap dress, and high heels, she heads off to a bar called Hurricane 26 in search for one of her attackers. Using her unique abilities to sense out the men who entered the club, she catches a whiff of the chlorine used by one of the men and even that metallic taste that was on the fingers of this very man. After flirting with him a bit, she lures him out to his car..quickly pulling a gun on him and orders him to drive off to a secluded location. They end up at a factory (which Lumen assumes is "abandoned enough" and leads him into a large room where she takes five shots at him, with only one bullet hitting his side.
Dexter in the meantime is working on his target, Lance Robinson, only to be constantly disturbed by calls from Lumen (whom he assumes has left the state by now) but finally takes an interest when he receives a message with a photo of a bloody man. He quickly calls Lumen to find out what that was, only to learn that she shot a man she believed to be one of her attackers (thinking the man to be dead as well) and this throws Dexter into a large problem: dealing with Lance AND Lumen's attempted murder. He leaves Lance wrapped in plastic and unconscious in the back of his car and goes to deal with Lumen.
Lumen rushes out to tell him what's going on and the two argue as he arrives at the scene of the murder, only to realize that the guy wasn't truly dead (though he lost a lot of blood). Dexter then goes on to ask Lumen the entire scenario, getting bits pieces while also examining the gun holes and a blood trail. They walk along following the trail, each learning more about each other and Lumen even discovering Dexter's true occupation as a forensics blood-splatter analyst. After a bit of controversy, they both find where the blood-trail leads and enter a separate building. The blood stops at this location suggesting the man is hiding somewhere and Dexter finds him beneath the grating, pulling him out and setting him against the wall.
Lumen proceeds to interrogate him as to the identities of the other men who raped her while Dan feigns innocence. He identifies himself as Dan the dentist and tries to convince Dexter that Lumen is crazy and has the wrong guy. Dexter becomes increasingly annoyed with her and this supposed "wild goose chase" until Dan the Dentist takes Lumen's phone and calls one of the other rapists and warns him of Lumen's survival. Unfortunately for him Lumen and Dexter both witness this and Dan shows his true colors calling Lumen a cunt. She then witnesses Dexter say "Die-Die" and snaps Dan's neck. Dexter says to grab the hose and start cleaning up the crime scene before the police arrive.
Lumen does this but then Lance wakes up and tries makes his escape, Dexter tells Lumen to leave which she does while Dexter deals with this mess. He gives her the keys to his old house and when she gets there she runs a bath. Dexter enters the house and unknowingly sees Lumen and they talk about his family, how he is a father and that there are still men out who raped her and that she won't rest until they are punished. Dexter, knowing he can't get revenge for Rita's death, tells Lumen he can at least help her get revenge for what happened to her and asks how many more are there, finally choosing to help her.
Later on, Lumen discovers that the men who raped her are trying to get rid of any evidence of their crimes which goes badly as five bodies are discovered and homicide is on the scene.
At the end of the season, after killing the final member of the Barrel Girl Gang (Jordan Chase), Lumen realizes that her darkness has left and she no longer can stay with Dexter. Dexter takes this rather hard as he was beginning to have serious feelings for her. Lumen indeed laid the final blow to Jordan Chase ending the vicious spree of raping/killing women. Shortly after Debra discovered the kill scene with Dexter and Lumen behind a plastic sheet. Having stirred up feelings of sympathy for the "barrel girls" Debra alerts (unbeknownst to her) Dexter and Lumen that she is going to call this in and they need to leave the area immediately. All this seemed to be a wake-up call for Lumen and she decided to leave Miami. The end of the show is Dexter at Harrison's 1-year birthday party, Astor comes up and asked Dexter where "the tenant" (Lumen) is. Dexter explained she left and Astor asked if he indeed helped her like he wanted, Dexter feels he did.
Two years later, Lumen is brought up again when LaGuerta is trying to prove that the Bay Harbor Butcher is still at work, and believes (for the most part correctly) that he killed the men who were part of The Circle. Debra later meets with Dexter to discuss LaGuerta's hunt. During the conversation, despite Dexter's insistence, she realizes (much to her disgust) that Dexter’s former tenant Lumen Pierce was his lover and partner in the murders of the men who had kidnapped and raped her. Dexter insists that none of this matters, and even if LaGuerta could figure out that it was Lumen and track her down, which was next to impossible, she wouldn't betray Dexter or incriminate herself.
- Robert Brunner - She intended to shoot him, however, Dexter intervened and informed her that he was not one of the men who raped her.
- Dan Mendell - Shot him at least once, but did not kill him. Later, Dexter snapped his neck, knowing he was guilty and deserved to die.
- Boyd Fowler - Killed by Dexter ("Practically Perfect")
- Dan Mendell - Killed by Dexter ("Everything is Illumenated")
- Cole Harmon - Killed by Dexter ("Take It!")
- Emily Birch - Killed by Jordan Chase ("Hop a Freighter")
Attempted to Kill Lumen
- Lumen is Dexter's second apprentice and the only one that is still alive as Miguel Prado and Zach Hamilton were killed.
- Lumen is from Minneapolis, MN. In the episode where her fiance shows up, they talk about their "beer runs in Madison". (This is because it is illegal to sell alcohol in Minnesota on Sundays, so beer runs to Wisconsin are a common practice of University of Minnesota students). Although the common practice is a beer run to Hudson, which is where the first liquor store is across the Wisconsin border. Madison is 269 miles away, Hudson is 27.
- The lumen (symbol: lm) is the SI derived unit of measure of the power of light perceived by the human eye.
- In medical terminology, a Lumen is referred to as a cavity or opening within a tube or a tubular organ.
- Lumen is the Latin word for Light or brightness, perhaps reflecting the enlightening effect the character has on Dexter and his personal Darkness.
- Lumen is one of the few major characters to have a known middle name.
- Lumen is currently the only other main protagonist in the series to have killed a main antagonist (Jordan Chase) other than Dexter. Dexter allowed her to kill him since Jordan was her main antagonist rather than his own. After season seven, Debra Morgan also holds this distinction.
- Lumen and Hannah McKay are the only surviving characters to know Dexter's secret, and Lumen witnessed it first hand. Some characters are mildly aware that Dexter has likely killed before, but Lumen and Hannah have extensive knowledge of his activities as a serial killer.
- Alex Tilden
- Boyd Fowler
- Cole Harmon
- Dan Mendell
- Jordan Chase
- Emily Birch
- Robert Brunner
- Barrel Girl Gang
- Towne House Motel
- Boardwalk Cafe
- Hurricane 26
- River Jordan Camp
- Baywater Marina Warehouse