Johnny Stool Pigeon (1949)

In San Francisco, during the 1940s, US Treasury agents interrupt an illicit exchange between a sailor and a drug dealer. During the shootout, the sailor is killed but the drug dealer escapes. Later on,the agents pick up the trail of the fugitive drug dealer but arrive at his apartment too late. The dealer lays dead, permanently silenced by a hired hit-man. The only thing the agents have is an address book found on the dead drug dealer's body. Among the clues there is one that seems to be promising: the address of a shady Canadian trading company based in Vancouver. Treasury agent George Morton decides to visit a convict in Alcatraz and solicit his help in infiltrating the underworld. Morton knows that convincing the imprisoned criminal Johnny Evans to become a stool pigeon for the Feds won't be easy. But Evans is Morton's only hope to infiltrate the underworld and crack the case.