A Breath of Suspicion — E.X. Ferrars / Elizabeth Ferrars

It is at a party that Richard Hendon first hears about the mysterious Paul Clyro and his unexplained disappearance. Clyro had been a scientist, doing secret work on viruses with a colleague named Wolsingham. But Wolsingham had committed suicide by swallowing potassium cyanide and Paul Clyro found the body, walked out of his house and vanished without a trace. Richard follows Clyro's trail - all the way to Madeira, where a man known as Gavin Chilmark is living a comfortable and contented life, free from any breath of suspicion...