Side Street (1949)

Joe Norson, a poor letter carrier with a sweet pregnant wife, yields to momentary temptation and steals $30,000 belonging to a pair of ruthless blackmailers who won't stop at murder. After a few days of soul-searching, Joe offers to return the money, only to find that the "friend" he left it with has absconded. Now every move Joe makes plunges him deeper into trouble, as he pursues and gets pursued through the shadowy, sinister side of New York.