At a secondary school in Harry’s neighbourhood, a burned-out teacher attempts to interest his class in Wuthering Heights. But class troublemaker, smart, mouthy Fergus shows what a hopeless task the teacher has.

Harry and Fergus have become local celebrities, and the murdered man’s widow approaches asking for help. She doesn’t believe his death was a suicide, and she’s accumulated evidence––her late husband’s body cam, and newspaper clippings announcing cryptic games. But Harry isn’t interested in any more cases. Kayleigh, she tells Fergus, was a one-off. She’s his tutor, not one half of a dynamic duo.

When a body is pulled out of the river near Harry's local pub, something about the dead man feels familiar to Harry. When she remembers how she knows him, she realizes she's stumbled onto the ultimate misdirect. Harry and Fergus go undercover, with the assistance of Harry's teenage granddaughter, Lola, to find the truth. Along the way, Harry starts to grow closer to Ray, Charlie's boss and mentor.

Harry and Fergus agree to help a local loan shark known as Happy find out who murdered his employee; in return, Happy will cancel the sizeable debt owed by Fergus's father. Harry notices links between the killing and Dostoevsky's "Crime and Punishment," which brings her to the attention of fledgling serial killer Billy Lund.

A stuffy dinner party in the home of Harry's former colleague goes awry when a vomiting bug hits all the guests but Harry. After the cause of the sickness is traced to a dead body in the home's well, Charlie's sergeant, Vicky Boyle, leads the investigation. Too eager to prove herself, Vicky makes some rash choices and zeroes in on Harry as the culprit, leaving Fergus to prove her innocence.

A violent storm traps Harry, Fergus, and Lola in the local pub. Cut off from the outside world by flooded roads and downed phone lines, the trio are put in even more peril when they discover a kidnap victim in a car. After freeing the man, they realize the kidnapper must be one of the handful of strangers trapped in the pub with them.

When a wealthy matriarch is strangled to death during a video call with her horrified relatives, the woman's daughter employs the services of the Wild/Reid Detective Agency. The agency being Fergus's brainchild, Harry is as surprised as anyone to discover it exists but agrees to indulge him. Money seems to be the motive for the murder, but everyone who stands to inherit was on the call.