At The Impossible, Cal double-checked the boiler pressure and fastened ropes to the rings at either end of the keel. She then coiled and fastened them to the floor of the gondola. The prince tied himself to the ring at the rear while Cal strapped in.

"Stand by to release mooring ropes." Cal cranked the fins out into position. The slight breeze tossed them about. "Release."

The Impossible floated up and clear of the warehouses. She hadn't topped up the hydrogen, so their buoyancy ...