Puzzles for Programmers and Pros

Part III: Faithful Foes

A gentle hand may lead an elephant by a hair.

—Persian proverb

The high-speed train from Montpellier to Paris hurtled through the French countryside at 300 kilometers per hour, but to Ecco and me this seemed way too slow. Ecco still held a tight grip on the note our bed and breakfast hostess had given us that morning—the message from Kate: "Jake, come to Paris immediately. Don't call. Rose has disappeared."

The vacation had started so well. Ecco and his French windsurfing pals had jumped the waves off Gruissan the day before. We spent the evening at the casino in town listening to a pair of beautiful folk singers. Ecco had planned to sleep late, because the best winds come up in the afternoon, but we were awakened by a loud knock on the door. "Monsieur Ecco, please wake yourself up," our hostess had said. "The woman Kate has left you a message."

Now we were on the train and Ecco had said hardly a word for the last hour. I, too, was deep in thought. Everything seemed so mysterious about this affair. For starters, why wouldn't Kate want us to call?

"She might think her phone line is tapped, Professor," Ecco said, apparently sensing my thoughts. "She doesn't want her daughter put in unnecessary danger. Rose has been climbing with her closest friends, so she wouldn't disappear on her own accord. Someone has done this to her."

"Has she been kidnapped?" I asked. ...