Avenger of Sins. SPECTR Series 3, #6

John Starkweather has one chance to stop a series of murders by the rogue telepath Ryan. Though only the drakul Gray and Night are safe from Ryan's mental manipulation, John knows it's up to him to capture his former friend-and fellow victim-before anyone else dies. But outwitting a telepath isn't an easy task. In order to bring Ryan in, John will have to confront the darkest parts of their shared past.
Because before all is said and done, John and Ryan find themselves confronting an even greater evil: one that will swallow them up body and soul.