I found A Man About a Dog, by Alec Coppel, in the back of a dim, dark secondhand shop (which oddly, or perhaps not so oddly, reminded me of the shop in The Painted Mirror episode of iconic 1970s horror series 'Night Gallery'). Published in London in 1947, the slim volume was in brand new condition and had probably sat untouched on a shelf for sixty years until its owner died.
Clive, a psychiatrist, is married to Storm, who has a lover, Bill. Storm also has a Scottish terrier, Montgomery:
'Montgomery was quite a lad. Jet black, relieved only by that flash of scarlet tongue, as worn by all the best Scotties, slightly protruding through the teeth.'Clive catches Storm and Bill in the act. Storm storms off, and Clive takes Bill at gunpoint to a place whose location is not revealed to the reader, or to Bill for that matter. Here, Clive restrains Bill via an ankle chain for some months, until speculation about his disappearance dies down sufficiently that he can be dispatched. For this purpose, Clive has an idea for a perfect murder: an acid bath.
So he tries it out.
Then he puts it into human practice.
But Storm is still on the scene, unaware of Bill’s fate. When she taunts Clive about other affairs, Clive produces Bill's teeth (his only remains) on a string and places them around her neck, telling her what he has done.
Clive then discovers a hidden microphone in the room, and mistakenly believes his game is up. As a last murderous act, he dilutes Storm's hot bath with enough acid to do to her what he did to Montgomery and Bill, while she is changing in her bedroom. In the penultimate scene, Storm drops her negligee to the floor, and poses one leg over the bath, about to step in.
And then a bell rings downstairs ...
A Man About a Dog, by Alec Coppel
Published by George G. Harrap, 1947, London
Don’t ask for it in your bookshop. Or your library. It disappeared years ago. I may have the only copy left. As far as reading goes, this kind of over-the-top horror, which is really black comedy, doesn’t so much rekindle an interest in reading as pour petrol on a raging fire. Quick! Get me another one!
Born in Melbourne, Alec Coppel attended Wesley College, where his English master might well have remarked on the correlation of the colour of Alec’s uniform and the nature of his prose. Coppel dropped out of medicine at Cambridge and wound up in Los Angeles, co-writing Hitchcock’s Vertigo among other films. A Man About a Dog was filmed as Obsession (released as The Hidden Room in the US) in 1949.