The door was slightly ajar.

‘It’s open,’ said Conor.

‘It’s open, hostage princess,’ Isabella reminded him.

‘Sorry, hostage princess. Let’s see what treasure lies inside.’

‘I’m not supposed to, Conor.’

‘Pirate Captain Crow,’ said Conor, slipping through the gap in the door.

As usual, Nicholas’s apartment was littered with the remains of a dozen experiments. There was a cannibalized dynamo on the hearthrug, copper-wiring strands protruding from its belly.

‘That’s a sea creature and those are its guts,’ said Conor, with relish.

‘Oh, you foul pirate,’ said Isabella.

‘Stop your smiling then if I’m a foul pirate. Hostages are supposed to weep and wail.’

In the fireplace itself were jars of mercury and experimental fuels. Nicholas refused to allow his staff to move them downstairs. Too volatile, he explained. Anyway, the fire would only go up the chimney.

Conor pointed to the jars. ‘Bottles of poison. Squeezed from a dragon’s bum. One sniff and you ’vaporate.’

This sounded very possible, and Isabella wasn’t sure whether to believe it or not.

On the chaise longue were buckets of fertilizer, a couple gently steaming.

‘Also from a dragon’s bum,’ intoned Conor wisely.

Isabella tried to keep her scream behind her lips, so it shot out of her nose instead.

‘It’s fert’ lizer,’ said Conor, taking pity on her. ‘For making plants grow on the island.’

Isabella scowled at him. ‘You’re being hanged at sundown. That’s a princess’s promise.’

The apartment was a land of twinklings and shinings for a couple of unsupervised children. A stars-and-stripes banner was draped round the shoulders of a stuffed black bear in the corner. A collection of prisms and lenses glinted from a wooden box closed with a cap at one end, and books old and new were piled high like the columns of a ruined temple.