Henri Charriere, born in 1906 and nicknamed Papillon for the butterfly tattooed on his chest, was a figure of the Paris underworld who admitted living as a pimp. In October 1931 he was convicted of murdering a fellow pimp, a killing he always denied, and was sentenced to life imprisonment plus ten years of hard labor in the penal settlements of French Guiana. His 1969 memoir told what happened next as a string of spectacular escapes: an open boat voyage to Colombia, months with an indigenous tribe, two years in solitary confinement, and a final leap from the cliffs of Devil’s Island onto a raft of coconut sacks.

This episode holds that memoir against the records of the French justice system. The files show a prisoner who spent his time as a nursing assistant in a colonial hospital, where he heard the stories of hundreds of other men. He did escape, but in 1944, by walking away from a mainland forest camp with four others and making his way to Venezuela. He was never held on Devil’s Island at all. The book sold more than one and a half million copies in France regardless, and in 1970 the state that had convicted him granted a pardon.

• Devil’s Island has no towering cliffs. It slopes gently into the sea, which makes the memoir’s climax a geographical impossibility.
• A former Paris Match reporter alleged that Charriere had been a police informant who tried to pin the murder on his own girlfriend.
• The French Justice Ministry reported that readers should divide the book’s claims by at least ten. The shark rescue of a guard’s daughter was the act of another convict, who lost both legs and died.
• In 2005 a 104 year old Parisian named Charles Brunier, who had a butterfly tattoo on his arm, said he was the real Papillon.
• Confronted with his errors, Charriere replied that he had not had a typewriter with him. Steve McQueen played him in the 1973 film, the year he died of throat cancer in Madrid.