Finn, Jake, and some friends attend a dinner with a mysterious host. However, the host then reveals himself as a murderous ghost that will possess the body of one guest to kill everyone else. The night turns from a masquerade party into a terrifying whodunit as the guests start to get murdered one by one.

Susan Strong returns and asks Finn and Jake to help fight off the Lub Glubs and regain her people's home in Beautopia.