We get the punch line a few pages later. An OSS officer has begun stockpiling European immigrants' clothing and storing it in warehouses with instructions that it not be dry-cleaned. Furst's purpose isn't to show off the information he has accumulated but to morally complicate the battle against fascism. He never questions the necessity of that fight, but he is forever illustrating the compromises and uneasy alliances inherent in it. The war exists in these books more as intimation than as fact.
People know that it's coming, and they choose to ignore it or to thwart it or to hasten it.
The secret lovers are, of course, Hitler and Stalin. That fairy-tale coda is delivered like a slap. Since the war, it has become fashionable to say either that communism was the only viable response to fascism or that communism was as bad as fascism. Furst pulls off the idea of Hitler and Stalin as comrades because he isn't an ideologue. He's not pitting one against the other to make a political point, just insisting on the inconvenience of facts.