London psychologist Dr. Frieda Klein suspects that Dean Reeve, the evil protagonist of French’s previous outing and “the nation’s favorite bogeyman,” is on the loose and out to get her. Frieda’s colleague DCI Malcolm Karlsson agrees to snoop around, but not before he investigates a decaying body, long dead, sitting propped up on the sofa in the Deptford house of Michelle Doyce. The house is a ghastly place boiling with flies and strewn garbage. All in a day's work for Karlsson, but not so much fun for Frieda, who finds herself plagued by the loss of her lover, Sandy, to New Jersey.

French may not achieve the level of suspense in Blue Monday, but the author tells a good story where everything that happens somehow relates to one or another missing person, where a reality-bending, twisted plot is the order of the day. Recently released from a psychiatric hospital, strong, pale-eyed Michelle was living with the dead body for five days or more. Only too willing to put her hotshot psychological skills to work, Frieda relishes the chance to play detective, convinced that Michelle is innocent of any crime.

Michelle’s talk of a delusional companion and of not knowing the difference “of being dead or alive” clearly indicates that she has a history of self-abuse. Prone to psychotic rants, she talks to dead men and stuffed dogs as if they can understand everything she says. As the investigation focuses on the estate bordering the Thames in London’s old docklands, the dead man’s identity becomes critical though he proves to be as elusive as Michelle’s opaque recollections.

With the action unfolding not far from her home, Frieda walks the streets at night, so tired she can hardly sleep. Attempting to sort through the murky emotions stirred up by Karlsson’s surprise reappearance, she’s shattered by news that bodily remains have been found floating in a storm drain in Bromley and may indeed be Kathy Ripon (a character from Blue Monday). Suddenly finding her past seeping into the present, Frieda recalls with trepidation the events leading up to the discovery of Joanna Vine as well as her own personal culpability in that case. Not one to let her insecurities get the better of her, Frieda busily plies the edges of Regents Canal looking for clues, finally acknowledging that Alan Dekker, Dean Reeve’s dead twin brother, is sucking her back into a vortex from which she may never return.

While the top brass in the London Constabulary remain convinced that Doyce must have killed the man, the investigation reveals him to be an enigma, a “creepy conman who became whoever people want him to be" and preyed on people’s weaknesses and their sadness at their failures. At first agreeing to use Frieda as a part-time adviser, Karlsson’s bosses then refuse to listen to her even though Karlsson is convinced Frieda is used to acts of confession and of listening to her patients’ “dirty little secrets.”

The true meat of the novel lies in the deceptive supporting characters: lonely neighbor Janet Ferris, who just wants someone to talk to about the dammed-up feelings inside her; Mary Orton, who tries to change her will, outraging her two adult sons; Frieda’s sister in-law, steeped in hypocrisy and denial; kindly Josef, who provides a pivotal clue to the case and gives Mary the confidence to expose her feelings; and Harry Welles, an ambivalent financial officer who forms a connection with Frieda but both confuses and interests her.

The streets, alleyways, and vanished waterways of Central London are pivotal to the novel’s core, though the tale is not so much a story about life in the city. More moody than a typical British police procedural, the plot focuses more on how Frieda aches for a settled existence and her personal struggle over how she uses people as "bait," especially the people she’s supposed to be caring for.