The man who dropped the blade on King Louis XVI in 1793 spent his evenings reading philosophy that argued against the death penalty. Charles-Henri Sanson, chief executioner of Paris, was born in 1739 into a hereditary office his great grandfather had founded. He wanted to be a doctor, but his school in Rouen expelled him in 1753 when it learned his father’s trade, and a stroke soon left that father paralyzed. By 15 he was doing the family’s work. At 18 he assisted at the drawing and quartering of Robert Francois Damiens, an ordeal so gruesome that his uncle quit the profession.

That horror shaped everything after. When the 1791 penal code required one method of execution for all classes, Sanson told the assembly why the sword would fail: blades dull, arms tire, and a botched stroke can start a riot. The guillotine removed the human element, and with it the friction that had limited killing. This episode follows Sanson through the Reign of Terror, where he oversaw nearly 3,000 deaths under successive governments, and examines a man who clung to procedure while privately despising political executions.

• The guillotine prototype was tested in April 1792 at Bicetre Hospital on straw bales and then live sheep, days before its first use on a criminal named Pelletier.
• Sanson demanded written orders before executing the king, then published his own newspaper account stating that Louis met the blade with composure and firmness.
• When a carpenter slapped Charlotte Corday’s severed head, Sanson reported him to the Revolutionary Tribunal and made clear the man was not his employee.
• On October 31st, 1793, he and his crew executed 21 Girondins in 36 minutes.
• He resigned in August 1795 and died in his bed in 1806. Sensational fake memoirs, with Honore de Balzac among the hired writers, appeared in the 1830s and were disowned by his son.