At a party, Felix picks “truth” during a game and is asked who he'd like to fulfill a fantasy with. He reluctantly chooses Gemma, embarrassing her and angering her boyfriend Chris, who punches Felix. Gemma breaks up with Chris and comforts Felix.

Months later, the group is invited to Felix’s surprise birthday party. They arrive at a mansion but are redirected by a groundsman to a remote shack, where they meet Felix’s older brother, Justin, a soldier with a hostile attitude. Justin claims Felix couldn’t make it, but soon reveals that Felix died by suicide after the Halloween party, leaving behind a postcard reading “Truth or Dare, bitch!”—a phrase Chris had used.

Justin blames the group for Felix’s death and traps them in the shack, demanding to know who wrote the postcard. When they try to escape, he shoots Paul and forces Luke to help restrain the others. Justin continues the “truth or dare” game with brutal consequences, including a deadly challenge involving water and battery acid.