The story is set in post-WWII Vienna, a city divided into sectors by the Allied powers. American writer Holly Martins arrives to meet his old friend Harry Lime, only to find out that Lime has died under suspicious circumstances.

Martins is told Lime was killed in a traffic accident, but as he investigates further, he discovers inconsistencies in the accounts of those present at the scene. A mysterious "third man" was seen helping carry Lime’s body, but no one knows who he is.

The Third Man was adapted for radio by Lux Radio Theatre and originally broadcast on April 9, 1951, on NBC Radio.