Rue chose to ascribe it to nerves. “Steady, girl,” she said to the ship, then to Percy, “Which nodule registered? Are we dropping or lifting to catch the Shifter?”

Percy examined the probe. “Lifting, captain.”

Rue picked up the speaking tube that connected her to engineering and pressed the button that would sound a bell there.

“Yes?” Quesnel’s voice was almost snappish.

“Prepare for a puff, chief engineer.”

“I don’t know about this. We’re pushing her.”

“She was made to be pushed or Dama wouldn’t have given her to me.”

“As you say, mon petit chou.” She heard Quesnel turn away from the tube and murmur into the hubbub, “It’s a lift, Aggie – have them stoke all boilers hot.”

There came the sound of Aggie yelling.

Quesnel returned to Rue. “Ready, chérie.”

“Here we go!” Rue hung up the speaker tube and turned to face Percy.

“Do it, Professor Tunstell. Now, please.”

Percy pressed the puffer button to give the balloon its boost.

They bobbed out of the Gibraltar Loop into the loose uncharted swirls of the Charybdis currents. The Spotted Custard’s balloon caved in at several points as the dirigible was buffeted in various directions at once. The gondola section shook. Prim, still seated in a chair on the main deck, gave a little squeak of alarm and dived to secure the tea things.

“Find that current, professor,” Rue ordered, her heart in her throat.

“Almost there, captain, a little higher,” reassured Percy, looking utterly terrified.

He pressed the puffer button again.

They rose, but the balloon began to collapse inward on the leeward side. The gondola lurched to starboard as the balloon caught one current, while the lower part of the ship caught another. The two halves were being torn apart. If they weren’t quick, the gondola could separate from the balloon entirely and they would spiral down to certain death far below.

“Not enough power,” yelled Percy.

Rue battled the tilt of the deck, reaching for the speaking tube, holding her hat to her head out of instinct. She lifted the tube to her mouth, pressing the alert.

“What now?” came Quesnel’s voice, oddly calm under the circumstances, only that extra French to his accent indicating stress.

“More heat to the boilers, please, Quesnel,” said Rue, forgetting to use formal address in her fear.

“Since you ask so nicely, mon petit chou,” was Quesnel’s pleasant reply.

Rue nodded at Percy. “Again.”

Percy gave The Spotted Custard another puff.

The ship rose up in a quick bob, hooked in and then…

Everything levelled out, the balloon returned to its chubby ladybird state, the gondola hung straight down as if it had never tilted. Everything went calm as a loon floating serenely on placid waters.