Gumshoe is a new series of architectural books that introduces an original approach to the writing of architectural history. Emulating the detective novel, the focus is on actual buildings rather than on speculative designs and theories. The style and form is fresh and scholarly but also easy and enjoyable to read. In Mysteries of a Communist Cave, the second book in the Gumshoe series, Lytle Shaw conducts an investigation of Oscar Niemeyer’s building for the French Communist Party’s (PCF) central committee in Paris. Designed in 1965, just as party theorists began to rethink many bedrock assumptions about representation, Oscar Niemeyer’s PCF building is a microcosm of the shifting political and architectural landscape of the 1960s. It is also a literal Marxist structure that can thus help us concretely picture just exactly what Structuralist Marxism might have been. Shaw draws out the PCF’s language and context one element at a time and puts the elegant curtain-wall building with its cave-like assembly hall into revelatory dialogue with interlocutors in film, philosophy, anthropology, and politics. Perhaps the ultimate mystery of the communist cave is that its owners have not more often and more powerfully presented their landmark building as the vivid source of imagery it could be for the kind of world the PCF might like to construct.