A group of astronauts undergo a simulated deep space mission, but their psychological well-being deteriorates as they question the nature of their reality.

400 DAYS centers on four astronauts sent on a simulated mission to a distant planet to test the psychological effects of deep space travel. Locked away for 400 days, the crew's mental state begins to deteriorate when they lose all communication with the outside world.

Forced to exit the ship, they discover that this mission may not have been a simulation after all...