He quit when a policy got good men killed. He found an ordinary life, a late-blooming love, and a promise he refused to risk with a kiss. Then the phone rang.

Dan Hale—retired British agent—knows the terrorist they call "the Tuner", a patient maestro who choreographs mass panic "in common time." When the Tuner's next performance points toward a London school and the music teacher Dan loves, he's dragged back into a trade he hates under rules he no longer obeys.

Armed with nothing but a pocket doctrine—"No acceptable delay"—Dan rewrites the playbook from the ground up: hinges over heroics, rehearsal drills over hero speeches, boredom as a weapon. As decoy bags, cloned passes, and ghost accounts tighten the net, the city turns into a score of doors, alleys, and river steps—each one a downbeat the Tuner can exploit.

To save a hall full of families—and the woman who finally said she loved him—Dan must outpace a system built to hesitate, face the stairwell that broke him, and change the beat before the applause. In a duel between policy and instinct, some wars are fought at the hinge.