During World War II British Intelligence loved to boast that it had managed to turn all German intelligence agents working in England into double-agents reporting false information back to Germany and doing other dirty work. ""Druid"" turns out to be the code name for the single Abwehr agent who never got ""turned""--a secret Mosley claims to have gotten from Kim Philby (who got onto it as a British Intelligence agent). In 1940 SS Sturmbannfuhrer Walter Huppenkothen, who was counter-seducing an Abwehr colonel's wife, Frau Kathie Pruck, was told in bed that there were traitors on Admiral Canaris' Abwehr staff. Fearful, Frau Pruck then revealed all to the Admiral, but could not know that the traitors had his blessing; subsequently he had her thrown into a sanitarium and driven mad. Huppenkothen, however, now suspected Canaris and decided to send his own man into England to unearth Canaris' traitors. His choice was Gwyn Evans, 25--son of a German-born woman, raised in a Welsh colony in Patagonia, member of two militant groups: Welsh Nationalists and Argentina's Nazi Party. Under cover of a Luftwaffe raid, ""Druid"" parachutes into the Welsh countryside, makes his way into Swansea, seeks out a pub frequented by BBC-staffers--and because he can sing like a bird, lands a BBC-related job. Meanwhile Kim Philby of SIS has become convinced that Military Intelligence (MI5) is far too smug about having turned agents; he's sure that someone has been sent on Druid's very mission and wants to find him before MI5 does. Druid's first success is to alert the Wehrmacht to the limited invasion of Dieppe, set for Midsummer's Day. . . while all other German agents remained mute about the raid. But Philby's Communist control, Ernst, has heard that one agent did report the gambit; so Philby is doubly eager to get Druid. Soon Philby is in Lisbon, running through international agents like raisins in a pie, tracking Druid and having a magnificent confrontation with a top German spy who has invented--out of whole cloth--an enormous intelligence apparatus and is selling its secrets to the Germans; he and Philby trade intelligence scraps like rival pool hustlers and finally Philby gets a purchase on Druid. What's more, a German agent trained with Druid recognizes him during a BBC show and Philby eventually closes in on him--and turns him into a KGB agent! Though none of this can be pinned down, it's laid out with impressive simplicity and has all the grab, still, of a first-class melodrama.