The storm strengthened, and the world grayed as rain poured down in gushing torrents. Pulses of lightning brought enormous cracks of thunder. The stream along the road rose and then overflowed, sending a sheet of water at the bike’s wheels.

Charles halted. “It’s too dangerous to drive,” he said. “We’ll have to hide below a tree and wait it out or walk to shelter.”

They got off the motorcycle and leaned it against the trunk of a ...