They’d almost done it. A group of friends, digging a tunnel from West to East Berlin to rescue dozens of men, women, and children. Above their heads, the Berlin Wall: 27 miles of concrete, fortified with metal shards, trip wires, and thousands of border guards armed with Kalashnikovs.

The group—German students—had been separated from friends, family, and lovers for months, ever since August 13, 1961, when the barbed wire dividing East and West Berlin suddenly appeared. Now, after weeks of digging the escape tunnel, the students had run out of money. Without cash for equipment and food, it was looking like they’d have to abandon their plan.