A British agent is sent to investigate a suspicious monastery on a remote Scottish island, but he is killed by the local fishermen. Then Steed, Gambit, and Purdey are sent to look into their fellow agent's death and to continue his investigation. It seems that at the end of the second world war an aeroplane carrying Germany's Greatest Treasure (whatever that may be) ended up there - and the monks turn out to be not particularly religious.
