S05E01 My Bad: Dexter must make a choice; Quinn stirs up trouble for Dexter but supports Deb.

Based on novels by author Jeff Lindsay, Dexter follows the life of Dexter Morgan, a charismatic blood spatter analyst who works in the forensics at the Miami Metro Police Department. On the outside, Dexter seems like the perfect guy -- he has a sister, Debra (Jennifer Carpenter), that adores him and a steady girlfriend, Rita, with two kids that look up to him. However, what they don't know is that Dexter moonlights as a serial killer, only he isn't your typical killer. Basing his life on the teachings of his foster father, Dexter only kills people who truly deserve it: he ensures that those who got away with horrible crimes will never kill again.

Based on novels by author Jeff Lindsay, Dexter follows the life of Dexter Morgan, a charismatic blood spatter analyst who works in the forensics at the Miami Metro Police Department. On the outside, Dexter seems like the perfect guy -- he has a sister, Debra (Jennifer Carpenter), that adores him and a steady girlfriend, Rita, with two kids that look up to him. However, what they don't know is that Dexter moonlights as a serial killer, only he isn't your typical killer. Basing his life on the teachings of his foster father, Dexter only kills people who truly deserve it: he ensures that those who got away with horrible crimes will never kill again.

Based on novels by author Jeff Lindsay, Dexter follows the life of Dexter Morgan, a charismatic blood spatter analyst who works in the forensics at the Miami Metro Police Department.

Based on novels by author Jeff Lindsay, Dexter follows the life of Dexter Morgan, a charismatic blood spatter analyst who works in the forensics at the Miami Metro Police Department.

Dexter finds himself in a strange new world when he attempts to hire a nanny for Harrison so he can continue to stalk and kill his next victim. Meanwhile, Debra, who takes the lead on a bizarre double homicide, is displeased when Batista suggests bringing in an annoying rookie officer who has her own theories on the case. Things heat up for Dexter when Quinn notices strange similarities between Trinity Killer suspect, ‘Kyle Butler’ and Dexter Morgan.

While attending a self-help seminar, Dexter and Lumen vet and stalk a violent killer; Debra gets into some unexpected trouble from the fallout of the Santa Muerte case, forcing Batista to make a difficult decision.

In the season finale, Dexters situation grows desperate when he discovers that Lumens been set up. Despite knowing hes being baited into a trap, Dexter risks everything to make sure he doesnt fall into the same mistake again. In the Barrel Girls case, Debra lets her personal feelings lead her instincts once she concludes that vigilantes are more than just a theory. Quinn finds himself in a troublesome situation, which only Dexter can help him out of.