Sarah Miller, a Boston archivist abandoned by her con-artist father as guarantor on a debt owed to a rival crime family, is extracted from a besieged parish vault by South Boston kingpin Cillian Brannagh, who needs her rare cryptographic skill to recover his stolen offshore ledger.

She negotiates a written bargain—full archive access and bodily autonomy in exchange for decoding his cipher—and in the process uncovers who is really siphoning his empire, discovers a legal instrument that may void her own debt, and slowly cracks the armor of a man who murdered the uncle who tried to poison him.

As their alliance turns to something neither trusts, a framed betrayal, a captivity, and a rival family’s assault force each test whether two people who built walls for a living can choose partnership over control.

Tropes: forced proximity, captor/captive to lovers, grumpy/sunshine inversion (two guarded protagonists), found leverage / negotiated bargain, protector hero, competence porn, touch-her-and-die devotion, wounded/traumatized hero, he falls first, enemies-adjacent to lovers, betrayal and grovel, only-one-bed intimacy, taking a bullet/poison for the other