The eighth season of Supernatural finds Dean (Jensen Ackles) in hot pursuit of Sam (Jared Padalecki) after escaping purgatory. He is shocked to realize Sam opted not to try and rescue Dean; rather, he has decided to live a normal life with his newfound girlfriend, a veterinarian named Amelia (Liane Balaban). Eventually, Sam returns to the cause to help Kevin Tran (Osric Chau), a prophet of the lord, translate the writing on a tablet that contains the instructions to permanently close the Gates of Hell. A twist of fate leaves Sam responsible for completing a series of trials that would close both Heaven and Hell, but the wildcard Metatron (guest star Curtis Armstrong), a former servant of God, has other plans in mind. Meanwhile, Castiel (Misha Collins) struggles to rid himself of Naomi (Amanda Tapping), an angel controlling Castiel from Heaven.

Marshall and Lily yearn for the luxuries of sleep and sex after the arrival of baby Marvin, while Barney tries to win the affections of both Robin and her much more intimidating father. At work, Marshall continues to strive to become a judge, and Ted tries to design his best building yet.

Nate Ford (Timothy Hutton), an expert thief who was once an insurance investigator, leads a down-and-out crew of people eager to get even with the rich and powerful individuals that contributed to their own financial ruin. Relationships among the group continue to evolve, while Nate struggles to come to terms with his place in the world. Elsewhere, Interpol agent Jim Sterling (Mark Sheppard) dedicates himself to apprehending Nate and putting a stop to his exploits.