A decorated detective inspector is murdered on the tranquil grounds of the St. Peter's Police Treatment Centre, shot through the heart with a crossbow arrow, and compromising photographs are discovered in his room. Detective Chief Inspector Alan Banks is well aware that he must handle the highly sensitive --- and dangerously explosive --- investigation with the utmost discretion.
Because the case may involve police corruption, an officer from Professional Standards, Inspector Joanna Passero, has arrived to work with Banks and his team. Though he tries to keep an open mind and offer his full cooperation, the dedicated Banks and his practical investigative style clash with Passero's cool demeanor and by-the- book professionalism. All too soon, the seasoned detective finds himself under uncomfortable scrutiny, his methods second-guessed.
As Banks digs deeper into the life and career of the victim, a decorated cop and recent widower named Bill Quinn, he comes to believe that Quinn's murder may be linked to an unsolved missing persons case. Six years earlier, a pretty 19-year-old English girl named Rachel Hewitt made national headlines when she disappeared without a trace in Tallinn, Estonia. Convinced that finding the truth about Rachel will lead to Quinn's killer, Banks follows a twisting trail of clues that lead from England to the dark, cobbled alleys of Tallinn's Old Town. But the closer he seems to solving the complicated cold case, the more it becomes clear that someone doesn't want the past stirred up.
While Banks prowls the streets of Tallinn, DI Annie Cabbot, recovered from her near-fatal shooting and back at the station in Eastvale, is investigating a migrant labor scam involving corrupt bureaucrats and a loan shark who feeds on the poor. As evidence in each investigation mounts, Banks realizes the two are linked --- and that solving them may put even more lives, including his own, in jeopardy.