Spaceman follows Jakub Procházka, a Czech orphan turned astronaut, who is sent on a solo mission to the edge of the galaxy to collect mysterious ancient dust. As he drifts further into space, Jakub must confront his past, his sanity, and the voice of an ancient creature that haunts his spacecraft. Faced with solitude and a crumbling marriage, he must find a way to return to Earth while keeping his mind intact.