Recently divorced career woman Alex Greville begins a romantic relationship with glamorous mod artist Bob Elkin, fully aware that he's also intimately involved with middle-aged doctor Daniel Hirsh. For both Alex and Daniel, the younger man represents a break with their repressive pasts, and though both know that Bob is seeing both of them, neither is willing to let go of the youth and vitality he brings to their otherwise stable lives.

In postwar Vienna, Austria, Holly Martins, a writer of pulp Westerns, arrives penniless as a guest of his childhood chum Harry Lime, only to learn he has died. Martins develops a conspiracy theory after learning of a "third man" present at the time of Harry's death, running into interference from British officer Major Calloway, and falling head-over-heels for Harry's grief-stricken lover, Anna.

A paraplegic baroness mistakes a man's pity for love - and tragedy ensues.