The synopsis: Adam (Leigh Whannell) and Lawrence (Cary Elwes) awaken in a sketchy, dirty bathroom, each chained to a pipe across the room from each other. Between them lies a corpse holding a gun and a tape recording from the "Jigsaw" killer that instructs Lawrence to kill Adam by six o'clock, or his wife and daughter will die. The only way for them to escape their chains? Using a pair of hacksaws to cut off their feet. So thoughtful of the killer to provide those!
The twist: A lot of complicated things go down, but basically Lawrence gets so desperate that he ends up sawing off his own foot, shoots Adam in the shoulder, and crawls out. After that, the corpse in the middle of the room casually gets up, revealing that the killer has been in the room with them the whole time. He turns off the light, yells "game over," and shuts the door, leaving Adam alone to die.
The amount of damage it'll do to your psyche: 🔪🔪🔪🔪🔪