Board Thread:Questions and Answers/@comment-6710985-20130224033903/@comment-83.83.28.123-20130918072334

She knew it because it was too easy to catch him in the end. An experienced arsonist giving himself away by having a kerosene smell around his house and suddenly passing out by the fumes. It seemed too good to be true to be plain luck. Combined with her knowledge that Dexter is very experienced with taking out serial killers, she easily deduced it was him who left Jensen for her.