Tell No One - Harlan Coben

Every year, the Doctor David Beck and his young wife, Elizabeth, meet at the same deserted lake to rediscover their love for each other, and inscribe one more year into 'their' tree. But that year was the last. Elizabeth was kidnapped and Beck knocked unconscious. By the time he woke up, his wife had been discovered dead, and horribly mutilated.

For eight years he grieves. Then one afternoon, he receives an anonymous e-mail telling him to log on to a certain web-site at a certain time, using a code that only the two of them knew. The screen opens onto a web cam and it is her face he sees.

This starts an inexorable chain of events as Beck tries to found out if Elizabeth is truly alive and what really happened that summer night. Soon he's a wanted man, as the FBI try to pin Elizabeth's murder on him, and everyone he turns to seems to end up dead...