With my hands and feet tied, keeping my balance was nearly impossible. The two of us wriggled on the floor like caterpillars, leaning into each other as we struggled—finally, painfully—into a sitting position.

That one basic movement drained what little strength we had. We sat back-to-back for a long time, each of us working at the rope on the other’s wrists.

Our arms were pinned behind us. We couldn’t see each other’s knots, only feel for ...