Disclaimer by Renée Knight is another debut novel by yet another British author fresh out of another fiction writing workshop.

Knight explains how she practiced writing a book about a character based on a friend of hers and an incident from their teenaged years: “At the end of the book I prepared to send it to this friend and thought how awful it would be if it was published and she read it without me having sent it to her first for approval. The idea chilled me.”

Disclaimer was released by HarperCollins this past May in cloth cover, and Knight turned that “chill’’ from thinking about her friend unexpectedly reading about herself into a claustrophobic, gelid psychological mystery about a successful woman, wife and mother who finds a novel on her nightstand with her as the leading character.

At first, before she began reading, the book was thought to have come into her new house as a gift, or maybe she bought it and forgot, or it belonged to her husband or her son and was mistakenly put with her books when they moved. Then she began reading, and her life would never be the same again.

I picked this book up, read some and put it down, three times. I’m one of those contemptible people who reads with pencil in hand, making notes of my impressions in margins and as a running narrative on the blank front pages.

Each time I picked up Disclaimer, I read 20 or so pages and put down the book after noting that the plot was still weak and characters still overwrought. But, with dozens of new mysteries waiting to be read, I picked up Disclaimer again and again, until finally I saw the brilliance in the portrait of the protagonist, Catherine Ravenscroft, and the stealthy subtlety of the claustrophobia building over the slow reveal of an impropriety of decades ago that should have remained closeted.

As it was, 25 years ago Catherine, Robert and their 5-year-old son, Nicholas, vacationed at a beach resort in Spain. Robert returns to London early for work and Catherine attracts the attention of a young man with a camera.

She’s flattered, maybe she returns the flirting. The two become friendly – he’s handsome and attentive, perhaps obsessed. Happily married to a loving and attentive lawyer, loosely attached to motherhood and willing to toy with being someone’s femme fatale, Catherine nonchalantly poses for the camera and forgets about Nicholas drifting out to sea in a plastic inflatable.

Finally, noticing the building waves and Nicholas’ dire straits, Catherine’s dogged admirer throws down his ever-present camera and runs gallantly into the churning ocean to save the young lad, certainly with assurance of unsparing praise. After observed and admired heroics, our lens peeper brings the plastic raft within safe distance of the shoreline help, then drowns.

Now, two and a half decades later, the mother of the drowned voyeuristic lensman and chivalrous lifesaver finally reaches the point of paroxysm over Catherine’s shameful antics captured in the photographs her son had taken during those halcyon days and nights in Spain. She writes The Perfect Stranger that Catherine finds next to her bed. Then the photos are delivered to her and to her son and to her husband.

This is a haunting story that builds like a dust devil into a destructive tornado that leaves no one undamaged. No matter your taste in storytelling, Disclaimer will pull strings you hadn’t known you had. And the ending … you’ll not forget the ending, perhaps ever. This book’s a keeper.

jeff@jeffmannix.com. Jeff Mannix is a local journalist and author.