Right You Are, Mr. Moto — John P. Marquand

In the final installment of John P. Marquand's classic espionage series, Mr. Moto returns -- 15 years after his previous adventure
 
After serving his country as a paratrooper in World War II, Jack Rhyce takes on an even more dangerous mission when he becomes a secret agent in the early years of the Cold War. Now he and fellow spy Ruth Bogart have been dispatched to Tokyo to foil an assassination attempt on a leading liberal politician. Murder is only the first part of this nefarious Communist plot; the ultimate objective is to stir up anti-American sentiment in a country that has formed close bonds with its former adversary in the West.
 
Undercover as do-gooders employed by the Asia Friendship League, Jack and Ruth are met at the airport by Mr. Moto, a would-be tour guide who offers to make their stay more hospitable. The American spies immediately suspect that there is more to Mr. Moto than meets the eye. But whose side is he on? To stop the cunning mastermind behind the sinister scheme, Jack and Ruth will have to learn the secrets of post-war Japan as quickly as possible. The mysterious Mr. Moto might just be their greatest ally, or their worst enemy.
 
First serialized in the Saturday Evening Post, John P. Marquand's popular and acclaimed Mr. Moto Novels were the inspiration for 8 films starring Peter Lorre.