"A masterful whodunnit " - Number 1 NY Times bestselling author Lisa Gardner The envelopes are addressed to simply "Katja" above the name of a Cambridge college, but no one by that name attends or works there. The early letters are desperate; the later ones are angry. No one knows who the messages are meant for, until a seemingly accidental death involves the police, who are already overwhelmed by an unidentified body in the fens. Detective...