Ashenden: Or the British Agent by W. Somerset Maugham
A playwright called Ashenden is recruited by Colonel R., a British Intelligence officer. He is sent to Switzerland where he becomes involved in a series of adventures. In one he accompanies a man called the Hairless Mexican to Italy, where a Greek agent of the Germans is to be assassinated. In another he must get an Italian dancer to induce her Indian lover, a German agent, to cross the border into Switzerland to see her, so that Ashenden can arrest him.