With events spanning both world wars, the tenth instalment in the Lane Winslow mystery series—which first began with the bestselling adventure A Killer in King's Cove—is a transatlantic tale of sibling rivalry, infidelity, and espionage.

It’s an early morning in May when Lane is pulled from a deep sleep by a concerning phone call from Scotland—her grandfather has had a heart attack. Lane hastily makes plans to fly overseas, and a dejected Inspector Darling prepares himself for a stint of bachelorhood. But before he can begin to dwell on it the Nelson Police learn that Ben Arden, a local cad, has gone out for a late-night boat ride and not returned, which immediately sets the town rumour mill churning.

In Scotland Lane finds her grandfather on the mend but her estranged sister Diana caught up in stressful—and mysterious—circumstances of her own. As Lane follows the thread leading from South Africa to Aberdeen to the War Office in London it becomes apparent that her sister is on the run, and that keeping secrets seems to be a Winslow family trait.

Back at the Nelson Police station a strange assemblage of clues begins to amass around the Arden case, stretching from the local printshop all the way back to the Great War. But progress is interrupted when the mayor himself issues a demand that Darling travel to England to tie up a decades-old mystery with local connections. True to form, upon Darling’s arrival in London he is quickly swept up in Lane’s mission, which threatens to endanger the entire family.