The Third Alibi

This is quite an intriguing murder mystery about a vain composer ("Norman") who has an affair with his sister-in-law ("Peggy"). When she becomes pregnant his wife ("Helen") refuses to divorce him so he and his mistress set about devising a cunning plan to be rid of her. It's quite a simple story, but told with plenty of twists and turns that keep the whole pot boiling nicely. Patricia Dainton is superb as the wife and John Arnatt as the slightly Priestley-esque "Superintendent Ross".