Post-war Paris brought a blossoming of culture and thought. The Nouvelle Vague transformed French cinema, young couturiers reinvigorated French fashion, existentialism flourished in literature and philosophy, and the city swung and swayed to a vibrant jazz and rock 'n' roll scene. In the middle of it all, was Paul Almasy. The well-travelled photojournalist, born in Hungary, had made Paris his hometown and spent his days and nights wandering its alleys,...