In a mural in Mexico City, John D. Rockefeller Jr., a lifelong teetotaler, sits in a nightclub nursing a drink beneath a rendering of syphilis bacteria. That petty revenge in plaster is the endpoint of this episode's story: the years 1932 to 1934, when Diego Rivera, a communist recently expelled from the party for taking capitalist money, was hired through Abby Aldrich Rockefeller to paint Man at the Crossroads in the lobby of the RCA Building at Rockefeller Center for 21,000 dollars, after Matisse was booked and Picasso never answered the telegram.

We explain why a true fresco chemically bonds to the wall, how Rivera quietly added a portrait of Lenin after a hostile newspaper article, and how a single drip of paint from workmen above led architect Raymond Hood to spot the face. Nelson Rockefeller asked politely for Lenin's removal; Rivera  ...