First published 1967; cover shown is the 1984 omnibus paperback from Penguin Books (UK).
Arthur Brownjohn is a bald, timid man living in the suburbs with his dominating bully of a wife, Clare. Major Easonby Mellon is a red-headed, promiscuous man running an unlicensed dating agency and living with his doting wife, Joan. Brownjohn and Mellon have nothing in common... except being one and the same person.
Arthur created the Mellon persona as an escape from life with Clare, an independently wealthy woman who constantly tells him what to do, embarrasses him in front of his friends and will not share her money with him. As Mellon, Arthur has acquired a bigamous wife, a string of lovers, and the excitement that his normal existence can not give him.
Arthur has spent years reading true crime cases and working out where criminals make mistakes. When Arthur decides to murder Clare in order to acquire her money, he realises he can create a "perfect" suspect. He will plant a few carefully written, increasingly desperate love letters from Mellon to Clare, and commit the murder dressed as Mellon.
Things don't get off to a good start when Arthur arrives at the house. Clare recognises her husband and demands he remove the wig, beard and "ridiculous" clothes immediately. The boldness Arthur always felt when in his Mellon persona disappears, and he quickly shoots Clare before escaping to set the rest of his plans in motion.
Arthur is not suspected at first, with the police following the Mellon lead. Instead of feeling relief or even guilt, Arthur discovers he can feel nothing at all. He sells Clare's house and moves to the country, in a vain attempt to rediscover himself.
When the police "prove" that Arthur used Mellon as a hired killer, his carefully researched plans come undone. In a final, ironic twist Arthur is charged with the murder of himself, and simply goes insane. This is an ingenious story of double identities, and reminded me a lot of Deathday by Angus Hall (1968), which Symons actually refers to in his novel, citing it as a true case.
Julian Symons (1912 - 1994) was a well respected English mystery writer and critic. He succeeded Agatha Christie as president of the Detection Club in 1976, and was one of the few English writers to be named a Grand Master by the Mystery Writers of America (in 1982).