Dortmunder agrees to do a dangerous favor for a gang of nuns.

It was supposed to be a simple caviar heist. Dortmunder is almost in the building when the alarm sounds, forcing him up the fire escape and onto the roof. He leaps onto the next building, smashing his ankle and landing in the den of the worst kind of creature he can imagine: nuns. Although decades removed from his Catholic orphanage, Dortmunder still trembles before the sisters' habits. But these nuns are kinder than the ones he grew up with. They bandage his wound, let him rest, and don't call the cops — for a price. The father of the youngest member of their order, disgusted by their vow of silence, has kidnapped his daughter, locked her in a tightly guarded penthouse apartment, and is attempting to convince her to renounce her faith. The nuns ask Dortmunder to rescue the girl. It's an impossible assignment — but one he cannot refuse.

Donald E Westlake