Synopsis: Tab Hunter plays a mentally unbalanced ex-con living in London, who is seen emerging from prison during the opening credits. His wife seems to have struck up a platonic friendship with Hunter's employer during his incarceration and their son (whom it appears Tab has never met) clearly looks at this "uncle" as a surrogate father.
It emerges that Tab's character murdered someone in a brawl (most likely convicted of man-slaughter given that he is being released after 5 years!) so his mental state has always been questionable, but the combination of dealing with the sudden onset of paternal resposibility, a love rival and the alienation he feels upon release lead to a tragic climax!
As one IMDB reviewer puts it "While it could be argued that Hunter overplays the giggling psycho somewhat, it works, in large part because the fine ensemble cast keeps the tension up without descending into hysterics, everyone pussy-footing around the clearly damaged dad."