400 days: This is the period of time set for a simulated space mission to prepare four young astronauts for an upcoming trip into space and to test their psyche. Sealed off from the outside world, the team is isolated in a remote bunker that acts as a space capsule. Soon, nerves are on edge as strange events accumulate within the bunker and contact with the control center is lost. What is still part of the experiment, what is not? The boundary between reality and madness threatens to crumble completely until the crew makes a momentous decision...