Holly Martins, a writer of pulp Westerns, arrives in post-war Vienna on the invitation of his childhood friend Harry Lime. But on arrival he finds that Harry has recently been killed by a car whilst crossing the street, leaving a grief-stricken lover, Anna. When local British investigating office Calloway claims that Lime was an unsavoury criminal, Martins accepts an offer from a local book club to stay in Vienna in order to clear his friends name. As he investigates his friends last hours, he grows closer to the doomed Anna, and learns of an unidentified third man at the scene of the accident, who may hold the key to the deepening mystery surrounding Harrys death.