Season synopsis
Contains spoilers for this season and earlier seasons.
Finn and Jake begin by trying to reach the Citadel, where Finn’s biological father Martin is imprisoned. Finn expects a reunion, but Martin is a self-serving escape artist who abandons his son as the Lich tears through the prison. Finn’s grass sword consumes his right arm as he tries to follow, and the Lich is transformed into the harmless giant baby Sweet P. The betrayal leaves Finn grieving both his missing arm and the father he had hoped to know. Other stories unsettle Ooo’s politics: Princess Bubblegum loses an election to the King of Ooo and retreats from the Candy Kingdom.
Late in the season, Gunter’s true nature emerges: he is Orgalorg, an ancient cosmic predator who steals one of Bubblegum’s ships and heads for a passing Catalyst Comet. Finn and Jake pursue him into space. Inside Orgalorg, Finn’s regrown grass arm becomes a weapon that damages the comet, where Finn meets a being that offers him the chance to ascend as a Catalyst Comet. Finn refuses because he wants to stay in Ooo. Martin appears in a space moth and accepts the offer instead, leaving Finn behind again; Finn and Jake return home, while Orgalorg is reduced to penguin Gunter.