That night, Gus lay awake, tensely waiting for the signal from Will. After what seemed a very long time he made out the shape of Will’s figure moving towards the door. Very cautiously, so as not to disturb the other two boys, he slid out of bed and crept to join him. Outside, they looked at each other.

‘You’re sure you want to do this?’ Will whispered. Already he was out of breath.

‘Yes. Come on,’ Gus said.

They tiptoed along the cloister and then down the passage that led to the rear of the building. There was a door and Gus felt a sudden shudder of disappointment. The door would be locked for sure. But Will led him into a small room beside it, which had a window.

‘I tried this earlier,’ he whispered. ‘It opens.’

He was right, but climbing out was a different matter. The sill was several feet off the ground and even with Gus’s help, Will struggled to hoist himself up, and when he was through he almost toppled to the ground, gasping with the effort. When he had recovered slightly they set off across the open space towards the ship, but Will had to stop every few yards, bending over with his hands on his knees, trying to catch his breath. By the time they reached the spot where the fence was partly broken he was leaning heavily on Gus’s shoulder and breathing in shallow gasps.

Undeterred, he reached up and gripped the top of the fence. ‘Give me a push up.’

He bent one knee and Gus stooped and gripped his leg and tried to lift him, but he was a dead weight. For a moment he scrabbled with his other foot in a last desperate effort, but then he let go of the fence and fell back onto the ground. Gus bent over him.

‘Come on, try again!’

Will only shook his head. In the moonlight his face was deathly white and Gus thought for a moment that he had stopped breathing altogether. ‘Leave …’ he gasped. ‘Leave me ….’

‘No! I’ll wait. You’ll be all right in a minute.’

The sound of voices brought him to his feet. Lights were moving in the space between the buildings and the ship. The voices were coming closer; lanterns were held high. Gus cast around him for a way of escape. He might have scaled the fence, but that would mean leaving Will. Then a voice he recognised shouted, ‘There they are! I told you! They’re over there.’

The voice belonged to Jack Murray.

Within seconds Gus and Will were surrounded. Two of the school porters were there, carrying lanterns, and with them was Mr Frobisher. Murray hung back, watching.

‘So!’ Frobisher said. ‘Trying to run away, were you? You’ll wish you’d never thought of the idea. Come on, get up! It’s no good pretending you’re ill.’