The Naked Edge (Michael Anderson, 1961)

George Radcliffe is the key prosecution witness against co-worker Donald Heath, whom he believes he saw running away from the building after their boss has been stabbed and robbed. Although Heath emotionally protests his influence and claims that he was secretly drinking in the boiler room when the crime was committed, he is found guilty and given a life sentence. Shortly thereafter, Radcliffe makes some wise investments, and he and his wife Martha become members of London society. However, their happiness is disrupted when a five year old blackmail letter is belatedly delivered to their home, Martha's faith in her husband is shaken as circumstantial evidence begins to build that he himself was the killer and has profited from the crime. The resultant distrust and suspicion threatens their relationship as Martha is torn between love for his husband and irrational fear.