Since France abolished capital punishment, in 1981, it has been nearly impossible to see a guillotine. In Paris, the Museum of the Prefecture of Police possesses just a guillotine blade, while the closest thing on view at the Carnavalet Museum is a two-foot-tall model guillotine and a pair of dangly brass guillotine earrings. In the Eleventh Arrondissement, where the Rue de la Roquette meets the Rue de la Croix Faubin, you can just make out five rectangular indentations in the pavement—flagstones that supported a guillotine that stood outside the Roquette prison during the second half of the nineteenth century. (It...