Their Little Secret, Mark Billingham

When DI Tom Thorne is called to conduct a routine assessment at the site of a suicide, he expects to be in and out in no time. But when he arrives at the metro station, where a woman named Philippa Goodwin threw herself in front of an underground train, Thorne inexplicably senses something awry and feels copelled to dig deeper. He soon discovers that she was the victim of a callous con-man whose deception plunged Philippa to her end.

Enraged that one man’s trickery caused an innocent death, Thorne enlists DI Nicola Tanner to help him track down the swindler and bring him to justice. But the detective duo gets more than they bargained for when a young man’s lifeless, bludgeoned body turns up on the shore of a nearby seaside town: it appears that very con artist they’re searching for is connected to the murder.