Season 6 starts with Dexter Morgan attending his 20th high school reunion to hunt a former Prom King. Everything's going perfectly for Dexter until Homicide comes up against a gruesome, faith-inspired murder. It leaves Dexter asking some bigger, spiritual questions about what to pass on to his son. Debra Morgan, in a solid place in her relationship with Quinn and in her role as detective, becom...

To solve a mysterious and macabre murder, Homicide brings in Brother Sam, a minister with a criminal past. But when Dexter meets Brother Sam, he doesn't recognize a man of God, but a fellow killer who might have found a cover even better than his own. Debra, now a local hero, is surprised by two life changing proposals.

Dexter is confronted with a sobering glimpse of his own potential future when a serial killer from his past makes a startling reappearance. Debra is uncomfortable in her new job. And Travis struggles to keep his mentor happy, as he and Gellar prepare their next twisted tableau, ensuring Debra's next task will be a daunting one.

Much to his own surprise, an emergency with Harrison has Dexter leaning on Brother Sam for support as he questions the idea of faith. But when Dexter is confronted with Gellar and Travis' next awful tableau, he is forced to ask if faith, in the wrong hands, is deadly. With proof of a religiously motivated killer, Homicide hunts for a zealot, with Debra giving her first official Press Conference...

With the help of his newfound friend, Brother Sam, Dexter wonders if there is light within him to counter the darkness. The search for the Doomsday Killers takes Dexter in a new direction, while Batista and Quinn pay a visit to the university where Professor Gellar taught. Due to departmental regulation following the shooting, Debra is forced to begin therapy.

Dexter is caught up in a very personal case that awakens the needs of his Dark Passenger. Meanwhile, Debra feels overwhelmed by her new Lieutenant duties, made all the more complicated when she finds out Quinn slept with a witness in the Doomsday case.

Dexter finds himself teamed up with a fellow Dark Passenger when he takes a road trip to Nebraska to tie up some loose ends from the past. As Debra continues to lead the investigation into the Doomsday killings, she deals with the complications of being a lieutenant.

Dexter uses lessons he learned from Brother Sam to follow up on some new leads in the Doomsday investigation. Debra butts heads with Captain LaGuerta over the case of a dead call girl.

Dexter finds help from an unexpected avenue while on the hunt for the Doomsday Killers, all the while trying to stay one step ahead of the Homicide Division. Debra continues to see her therapist and discovers something new about herself.

Dexter tries to figure out the Doomsday Killers’ next victim before it’s too late. Debra has a strong reaction to a crime scene, which leads her to the realization that she leans too heavily on her brother.

Dexter finds that in order to catch the Doomsday Killers, he must follow in their footsteps and create a macabre tableau of his own. Debra’s battle with LaGuerta over the case of the dead call girl boils over. Debra’s therapist makes an unnerving suggestion.

Dexter and the Homicide Division race against a lunar eclipse to catch the Doomsday Killers before their final gruesome act. Debra struggles with, but finally faces up to, a new emotional reality.