Successful surgeon Tomas leaves Prague for an operation, meets a young photographer named Tereza, and brings her back with him. Tereza is surprised to learn that Tomas is already having an affair with the bohemian Sabina, but when the Soviet invasion occurs, all three flee to Switzerland. Sabina begins an affair, Tom continues womanizing, and Tereza, disgusted, returns to Czechoslovakia. Realizing his mistake, Tomas decides to chase after her.

Operation Danube was the cover name for the invasion of Czechoslovakia by Warsaw Pact armies in August 1968. The fleet of Polish tanks which arrive to liberate their neighbor, ostensibly threatened by a counter-revolution, includes the old tank nicknamed Ladybird, which is the last to leave the barracks.