"Alfred Hitchcock Presents" The Derelicts (1956)

A year ago, Mr. Sloane lent Ralph the money he needed to develop and market a new invention, in return for 50% of the profits. Now Sloane calls Ralph to ask for his share, but Ralph has spent all of his earnings on his attractive, materialistic wife. When Sloane insists on payment, Ralph kills him in a park and takes his wallet, expecting to recover the IOU he had written. But the murder is witnessed by a vagrant, who also recovers the IOU in Sloane's cigarette case. The vagrant and a friend come to confront Ralph, demanding heavy payment in return for their silence.