Jarlath "Jar" Costello's girlfriend, Rosa, committed suicide when they were both students at Cambridge, and Jar has thought about her every day since. It's been five years, yet Jar is still obsessed with the idea that Rosa, the one true love of his life, is alive. He's tormented by disturbingly real sightings of her--experiences the psychologist treating him describes as "post-bereavement hallucinations." When Rosa's aunt uncovers an encrypted file on her laptop that she believes is Rosa's diary, she gives Jar the hard drive, sending him on a frantic quest to unlock the mysterious document and finally make sense of the suspicious circumstances surrounding Rosa's suicide. But the deeper he digs, the more confused he becomes as he is pressed into a dark underworld where nothing is as it seems and no one can be trusted. When a startling discovery convinces him more than ever that these are not just hallucinations--that Rosa really is alive--Jar is thrust into the heart of a larger intrigue that may finally shed some light on Rosa's death--even as it dangerously threatens his own life.