Captain Carey, U.S.A is a film about a former OSS operative, Captain Carey. After the war, he comes back to Italy to retaliate the death of resistance worker Giulia. Unexpectedly, Carey finds that his dead lover is actually alive and on top of that is the wife of a powerful Italian nobleman. Then, he unfortunately finds out that the far-from-grateful Italian villagers hold the Americans responsible for their current financial difficulties. Through all this, Carey sticks around, wanting to wash out the traitor who was responsible for the wartime deaths of many of his OSS colleagues.