The Third Man (1949)

In the post-Second World War, the unemployed pulp fiction writer Holly Martins arrives in Vienna to meet with his old friend from school, Harry Lime, who has offered him a job. On his arrival, he learns that Harry has just died; he was hit by a truck in front of his building, and he goes to his funeral. Holly Martins sees a beautiful woman, Anna Schmidt, and a friend of Harry, and sooner he learns that Anna was Harry's lover. Maj. Calloway, who is commanding the investigation, offers the ticket for Holly to return home, but while waiting for the trip, he talks to two friends of Harry who tell him that they were the first to help his friend. However, the porter of Harry's building says that there was a mysterious third man who helped Harry, and Holly Martins becomes intrigued by the inconsistency and decides to investigate further. Sooner, he discloses that Harry Lime was the leader of a gang that robbed penicillin from the military hospital to adulterate and resell it, which has caused the deaths and anomalies in many children. He continues to investigate, and he has a great surprise when he finds out who the third man is.

IMDb: https://www.imdb.com/title/tt0041959