A man is trying to escape from the titular Cube. Upon entering a trapped room, he is sprayed with a liquid that rapidly melts his entire body. The rooms in the Cube are being monitored from a remote observation room by two technicians, Eric Wynn and Dodd, who are unaware of who their employers are. The pair are shown playing chess during work, whereupon Wynn demonstrates mental calculator abilities which he uses to predict Dodd's moves. Wynn has also a hobby of drawing comics that portray him and Dodd as superheroes.
A group of strangers awaken in a gigantic, mechanized cubical structure of unknown purpose and origin, made up of numerous smaller cubical rooms. Each room has six doors, one on each face of the cube, which lead into adjacent, largely identical rooms.Some of these rooms are "safe", while others are equipped with deadly booby traps.