Dexter must make a choice; Quinn stirs up trouble for Dexter but supports Deb.

Dexter tries to get the lives of his family back on track by temporarily curbing his dark urges, but is forced to reconsider after he makes a horrific discovery. Meanwhile, Debra finds it difficult to keep her private life private while sharing her apartment with Dexter and the kids.

Dexter tries to hire a nanny for Harrison so that he can continue his "extracurricular activities." Meanwhile, Debra is paired with a rookie detective on a double homicide and Quinn starts to piece similarities together between Dexter and his alias, Kyle Butler, a suspect in the ongoing Trinity Killer investigation.

Dexter finds himself in a strange situation when, instead of taking a life, he has to save one. Deb has a scary confrontation with a key suspect in the Santa Muerte murder cases. Quinn continues following up on the strange similarities between 'Kyle Butler' and Dexter Morgan.

When Dexter is saddled with an unwanted conspirator, he is forced to make some hard decisions about her fate; meanwhile, Dexter wonders if Rita's death has awakened a darkness inside Harrison; due to Quinn's recent suspension, Debra works the Santa Muerte case alone, leaving Quinn time to enlist an old friend to look into Dexter.

Trying to get his life back on track, Dexter hunts a new target, but is distracted and drawn into a precarious situation while helping his troubled acquaintance; Batista discovers an interesting lead in the Santa Muerte murder cases; Quinn learns some new information about Dexter from a questionable source.

While helping Lumen, Dexter finds himself on a collision course with Debra and the rest of Homicide when he is called to investigate a horrifying crime scene; the Santa Muerte case leads to a violent standoff between Debra and the killers.

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.

While in the midst of hunting down their next victim, Dexter and Lumen are surprised by the return of an unannounced guest; Debra is assigned to the file room, but still manages to uncover new evidence in the Barrel Girl case.

Miami Metro uncovers more evidence in their ongoing investigations, and Debra names two suspects. Dexter, meanwhile, comes across a possible ally.

Dexter and Lumen's plans are momentarily thwarted when Dexter's forced to do damage control after he concedes that someone, outside of Miami Metro, has taken an interest in them. Debra's speculation on the missing Barrel Girl suspects begins to take shape. Quinn finds himself more involved in a homicide than he'd like to be.

In the season finale, Dexter's situation grows desperate when he discovers that Lumen's been set up. Despite knowing he's being baited into a trap, Dexter risks everything to make sure he doesn't 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.