Berlin. 1963. The height of the Cold War and an early morning spy swap. On one side of the trade: Martin Keller, an American physicist who once made headlines, but who then disappeared into the English prison system. Keller's most critical possession: his American passport. Keller's most ardent desire: to see his ex-wife Sabine and their young son. But Martin has questions: who asked for him? Who negotiated the deal? From a master of the form and heir to John LeCarré.