Calista "Cal" Wrenfield is the youngest magical notary in Brindlemoor, and she has one spotless record: not a single clause signed wrong. So when a routine lease notarization at the Ember Kettle Inn ends with her seal blazing across an ancient scroll, she is certain someone has set her up. The scroll is a Hearth Contract, a one-year engagement that only wakes for a seal that has never made a mistake. Her perfection is exactly what triggered it.

Havel Ormsgard, the dragon-blooded owner of the inn, takes the news with infuriating calm and a fresh pot of tea. The contract cannot be broken by force. If Cal walks away, her seal burns and her license goes with it. If the two stay too far apart, the magic of the inn, and of the whole city, begins to fade. So they share a roof, a thermostat war, and a scroll that keeps adding new clauses on its own, from sharing an umbrella to sharing a breakfast table.

Surrounded by nosy neighbors, a matchmaking young tea assistant, and a warm, all-knowing kitchen matriarch, Cal and Havel slowly uncover what the other hides behind the paperwork and the politeness. Cal believes every promise hides a trap. Havel believes he is a burden people eventually leave. Meanwhile, Brindlemoor's magic, which runs on promises freely kept, is quietly draining away.

When the contract's true exit clause finally surfaces, both have fallen in love, and neither dares to ask the other to stay. To save the inn, the city, and each other, Cal must face a secret older than the scroll and write the one promise she has always feared: a promise she chooses herself.