Matt Helm - The Shadowers  (English, Paperback, Hamilton Donald)

In order to foil a mass assassination plot, Matt Helm must undertake his most dangerous mission: matrimony. An agent like Helm might be a nice man to live with for a while, be he's not the kind a woman would marry. Unless she has too. Unless it's all part of maintaining an ingenious cover. The man whose daily bread is violence takes a most unlikely bride - just to make sure death doesn't part them.