Istanbul, 1761. Master Ihsan has built clocks for two sultans, a French ambassador, and one Venetian spy who paid in advance and never returned. His shop under the aqueduct keeps the truest time in the empire, which is why the palace messenger comes to him at dusk, with a purse of gold and a commission written in a careful, anonymous hand. A clock. The finest materials. The face inscribed in silver. And the mechanism built so that the hands run backwards — precisely, beautifully backwards, losing a day every day. "For whom?" asks Ihsan. "That question is not part of the commission," says the messenger. Gold is gold, and curiosity, as Ihsan's late master used to say, is a tax the clever pay to themselves. He builds it through the winter: reversed escapement, mirrored numerals, a tick that sounds, to his trained ear, like a heart unlearning its habit. It is the strangest and finest thing he has ever made. The night it is finished, before the messenger returns, Ihsan does what any master would do. He winds it, sets it by his truest clock, and watches it run. At midnight exactly, the backwards clock chimes thirteen — and from somewhere beneath the aqueduct, very faintly, something chimes back.