London, 1941. Britain has endured the relentless bombing campaign of the Blitz and emerged, scarred but unbroken. Caitrin, too, strives to weather each challenge that comes her way, though her ever-ready banter belies deep heartbreak and loss. But now the war has entered another phase. Instead of indiscriminate bombing, the Luftwaffe is pinpointing historic targets, including cathedrals and ancestral homes. It's as if Germany plans to erase Britain's very essence and culture, destroying morale as it does so.

Caitrin is no fan of the landed gentry, even if her fellow operative and friend, Lord Hector Neville-Percy, is one of them. But soon it is not just historical targets under attack, but hospitals and nursing homes too. Tasked with rooting out the saboteurs placing the beacons, she finds that all roads lead to Daniel "Teddy" Baer, a charismatic Whitechapel crook with high aspirations and zero scruples.

As a member of the female-driven 512 counterespionage unit, Caitrin understands how often women are underestimated and overlooked—and how to use it to her advantage. But she is not the only one who knows how to hide in plain sight, how to outwit and effortlessly manipulate. And sometimes, as with a beacon hidden deep within a building, danger only becomes apparent when it flares to life, right before the moment of impact . . .