Horse Under Water by Len Deighton

The Ipcress File was a debut sensation. Here in the second "Secret File," diving, drug trafficking, and blackmail all come together in a compelling story in which the dead hand of a long-defeated Germany reaches out to Portugal, London and Marrakech--and to all the neo-Nazis of today's Europe. The story as powerful today as ever, and the returning hero from The Ipcress File remains just as compelling as before. But now, he must now draw on all his resources when he's plunged into a story of murder, betrayal, and greed that's every bit as murky as the waters off the coast of Portugal, where the answers lie buried.