The discovery of the decapitated heads of seven French Trappist monks in Algeria in May 1996 shocked France and provoked a great outpouring of public emotion. Over 10,000 people gathered in Paris’s Place du Trocadéro to show their solidarity with the murdered monks. Earlier that year, in March, the monks had been abducted from the Tibhirine monastery in the Atlas mountains by a group of 20 armed men. For many, their decapitation also marked the climax of Algeria’s civil war between Islamist rebel groups and the Algerian government. The monks’ bodies were never found, which raised questions about who had...