Suddenly Frida felt the submarine slowing, and she nearly lost her footing as it rounded a corner. The captain signaled a full stop.

“Roger, I mean Dieter, what’s going on? Why are we stopping?” Frida instinctively wrapped her arms around his shoulders, the only familiar things in this place.

He shook her off brusquely and whispered in German, “We’re surfacing. Get ready to disembark.”

This definitely didn’t seem right at all. “I… I thought we were going to blow up a dam,” she said. The man’s whole demeanor had changed.

“Did you really think we’d make it all the way to Geesthacht in a stolen U-boat? We’re traveling by land from here on. There’s a truck waiting at the dock. Get in the back and keep your head down. We’re driving through Hamburg tonight. You will talk to no one. Get out. Now.”

Frida climbed the ladder and stepped onto the deck. Sure enough, a truck emblazoned with swastikas was idling nearby with its headlamps off. She didn’t see any explosives for the mission. “Keep moving,” said Dieter.