The Shadowers (The Matt Helm Series‪)‬

In order to foil a mass assassination plot, Matt Helm must undertake his most dangerous mission yet: matrimony.

An agent like Helm might be a nice man to live with for a while, but he’s not the kind of guy a woman would marry—unless she has to in order to maintain an ingenious cover. The man whose daily bread is violence takes a most unlikely bride—just to ensure death doesn’t part them.