A naked man appears from the sea at night on a lonely beach and interrupts another naked man's illicit love tryst: Innes was a master of a startling and intriguing opening (apart from many other things). This book, although very different in tone from much of what he wrote, is one of his best. It's a chase thriller in the John Buchan tradition, which Innes explored several times, and while being nothing like "real life", it is...
still much more convincing and, well, sombre (complete with a downbeat ending) than Innes's fans have come to expect.
There are some interesting psychological motivations here, and a lot of the tension is derived from the uneasy relationship between the two main characters, which gives the plot an additional edge.