The Cyclotron is a thriller that takes place at the end of the Second World War. Simone, a spy working for the Allies is entrusted with the mission to find and execute Emil, a scrupulous Berlin scientist who discovered before the Americans the way to build an atomic bomb, and is fleeing with his secret. Simone finds him on a night train speeding towards Switzerland. German soldiers, led by König, a German scientist, who want to arrest Emil and make him talk before he leaves the country, are also chasing him. The chase gets complicated when memories of love get intertwined and when it is discovered that there is somewhere on the train, a prototype of the bomb.