In September 2004, French police discovered a hidden chamber in the catacombs under Paris. It contained a full-sized movie screen, projection equipment, a bar, a pressure cooker for making couscous, a professionally installed electricity system, and at least three phone lines. Movies ranged from 1950s noir classics to recent thrillers.

When the police returned three days later, the phone and power lines had been cut and there was a note on the floor: “Do not try to find us.”

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