Untraceable - Jake Cross

An ex-special forces officer comes out of hiding to solve his sister’s murder in this tense mystery thriller.
 
When Matt Armstrong learns that his sister has been murdered, he returns to London to find out what happened. Visiting the place where their sister’s corpse was found, Matt struggles to uncover any information. But when he learns that a camera might have been used to record the killing, he becomes a man on a mission.
 
Together with his former girlfriend, Matt chases down every scant lead, finding one dead end after another. Then an anonymous tip changes everything he thought he knew about his sister’s life—and how it ended. Now Matt is hunting for someone who’s disappeared without a trace. But Matt knows a thing or two about disappearing . . .