Henry Deeping and Kate Meacham seem to clash every time they meet. Kate is frustrated by the change in her status following the death of her grandfather, a legendary figure in diplomatic circles. As a lone single woman, she is now effectively nobody, even though she knows everyone and has made important contributions to diplomacy in the past. Henry, just joining the Foreign Office, is wondering how to make his mark.
They agree to an exchange—Henry will serve as Kate’s escort to important events to which she is no longer invited, and Kate will introduce him to the important people she knows so well. But when they spot a foreign agent they thought had been apprehended, they decide to investigate on their own, enlisting a motley group of friends and relying on each other to uncover the truth.