Season Four
Big Bad
The Trinity Killer
Little Bad(s)
Vacation Murderers
Christine Hill
Air Dates
Premiere: 27 September 2009
Finale: 13 December 2009
DVD: See:Dexter DVDs
Blu-ray: See:Dexter DVDs
Guest Star(s)
John Lithgow as Arthur Mitchell
Keith Carradine as Frank Lundy

The fourth season the Showtime series DEXTER premiered 27 September 2009.

It focused on Dexter Morgan attempting to find his way to balance his family life, the birth of his son, and his "extra-curricular" activities.

The season opener was leaked to the Internet ahead of schedule in late August 2009


The fourth season received positive reviews before airing, including one from Michael Ausiello of Entertainment Weekly, who saw the fourth season as being "bloody promising." The New Yorker's Emily Nussbaum called John Lithgow's characterization of Arthur Mitchell as "so creepy I’m still not over it."

Official US DVD Synopsis:

"The Fourth Season brings not just one, but two new arrivals - a Harrison Morgan and The Trinity Killer. The groundbreaking and critically acclaimed original series by Showtime, starring Golden Globe winner Michael C. Hall, returns on DVD with all 12 thrilling and riveting episodes.

America's favorite serial killer has gone from freewheeling bachelor to responsible husband and doting dad. Maintaining an average-guy facade while satisfying his need to kill has never been easy. But now, with wife and kids in tow, Dexter's got more to lose than ever, as he gets drawn into a deadly game with a killer every bit as dangerous - and conflicted - as he is."

Season Four Synopsis

Dexter has married Rita and moved into a new house in Kendell. Adjusting to domestic life with her two children and their new baby, Harrison, proves difficult for him. Although, he continues to act on the urge to kill, the strain of his double life affects both his job at Miami Metro Police and his home life. Rita realizes that Dexter is lying to her, including that he secretly kept his waterfront condo, and they end up seeing a marriage counselor.

The police investigate a series of crimes called the "Vacation Murders." Retired FBI Special Agent Frank Lundy returns to Miami to follow a case that the FBI refused to handle. He calls the man he seeks the "Trinity Killer." This is because he murders three people in the same city roughly once each year and in a specific sequence. First, a young woman is killed in a bathtub, then a mother killed by falling, and lastly, a father is bludgeoned. The first two of this pattern recently happened in Miami, and Lundy wants to prevent the third killing. After rekindling their relationship, both Lundy and Debra are shot. Debra survives, but Lundy's wounds are fatal. The police assume the shooting was committed by the "Vacation Murderer."

Dexter steals Lundy's records, and finds the building where Trinity is expected to bludgeon a man. He observes Trinity on the security monitor in the act of killing his third victim. Dexter follows the killer to his home, and is astonished to learn that he is Arthur Mitchell -- husband, father, church deacon, and leader of the "Four Walls One Heart" charity organization. Dexter continues to watch Arthur, hoping to learn from him how to balance his killings along with his family life and career. Using the alias "Kyle Butler," Dexter joins Arthur's church, and befriends him. Meanwhile, the Miami police learn that the Trinity Killer places a small amount of cremation ashes at each murder scene.

After Dexter accidentally kills the wrong man, Arthur takes Dexter on a weekend trip to Tampa where he shows him the house in which he grew up. This is where, at age ten, he saw his older sister, Vera, die after he surprised her in the bathroom. Vera fell through the glass shower door and fatally severed her femoral artery. Dexter later stops Arthur from jumping off a building to commit suicide. Dexter learns that Arthur's killing pattern represents the deaths of Arthur's sister, mother, and father, and that Arthur has been using the Four Walls One Heart program to cover his tracks. Dexter discovers that Arthur's home life is not as delightful as it appears, as he abuses his son and locks his daughter in her bedroom. When things get violent at Thanksgiving dinner, Dexter forcibly prevents Arthur from hurting his family. Arthur realizes there is more to Dexter than meets the eye.

Obsessed with solving Lundy's murder, Debra notices that the angle of her wound indicates that the shooter is much shorter than Trinity. Trace evidence determines that Christine Hill, a reporter and Joey Quinn's girlfriend, is Trinity's daughter. To protect him, Christine took it on herself to shoot Lundy and Debra when they got too close to finding out Trinity's next target. After Arthur rejects her, Christine confesses to the crime and shoots herself in front of Debra. The police narrow down the list of suspects for Trinity, and Dexter realizes that he needs to move fast to kill Arthur.

Dexter follows Arthur and observes him abduct a young boy from an arcade. Dexter realizes that Lundy missed this part of Arthur's pattern. Each of Trinity's kill cycles was preceded five days before by the abduction of a ten-year-old boy. Since the children's bodies were never found, they were not recorded as killings. With the help of Arthur's son, Jonah, Dexter tracks down a bomb shelter where Arthur had kept the boy. Dexter is able to stop Arthur from burying the boy in cement at a Four Walls One Heart construction site, but Arthur escapes. Dexter, as "Kyle," blackmails Arthur with the threat of exposing him as a pedophile. Arthur, while looking for "Kyle," kills an innocent man with the same name. Arthur then tricks Dexter to reveal himself, and follows him back to the police station. They confront each other and Arthur learns Dexter's true identity.

Dexter tails Arthur to a bank parking lot. He sneaks up on Arthur, injects him with M99, takes his money, and prepares to take him elsewhere. However, having sideswiped another car during the pursuit, Dexter is confronted and taken to jail. Dexter is shortly released, but finds that Arthur has disappeared. Dexter arranges a getaway for Rita and his children to the Florida Keys as a means to protect them from Arthur, promising to meet them later in the day.

Arthur picks ups his car and it later breaks down, due to Dexter removing the oil cap. Dexter approaches Arthur, chokes him until he passes out, and takes him to the same bomb shelter to kill him. After disposing of Arthur's remains and the evidence, Dexter returns home, and finds a voice mail from Rita. He proceeds to call her back, but her phone rings inside the house. Hearing baby Harrison's cries, he runs into the bathroom to find Arthur's last victim, Rita, dead in the bathtub with a sliced femoral artery, and Harrison sitting on the floor in a pool of blood.

For more info, see:

Main Cast

Recurring Cast

Special Guest Star

Guest Cast

Dexter's Victims

  1. Benito Gomez
  2. Zoey Kruger
  3. Jonathan Farrow
  4. Stan Beaudry
  5. Arthur Mitchell



Episodes: 2009

Seasons of Dexter
Season 1
Season 2
Season 3
Season 4
Season 5
Season 6
Season 7
Season 8

Start a Discussion Discussions about Season Four

  • Trinity Killer...some confusion.

    20 messages
    • Trinity killed specific people in very specific ways. Rita being blonde and a mother of 3 made no sense to be killed by Trinity in the bathtub....
    • Hi Ribsplitter. Arthur didn't appear to be "falling apart at the seams" when he cooly strolled into the Miami Metro Pol...
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