Aimee smiled. ‘The White Lady members will look after me,’ she told him.

Colette nodded. ‘That’s how I know you’ll be safe.’ She pointed at a spot on the map. ‘There is the village of Cléry. The priest there, Father Gaulle, is one of us. He will see you safely home.’

Aimee smiled. ‘It will be an adventure, Marius,’ she said.

He gave a feeble nod.

Captain Ellis stood up and said, ‘I have to go now. I may not see you again, Marius. Good luck.’ They shook hands and the captain made for the door. ‘You have two backpacks,’ Aimee reminded him and picked up the one that had been by his left foot. She handed it to him.

‘Thanks, Aimee. This one is a little trap for your friend Silver Hand. It’s plans and a report on the weakness of the Whippet tank – exactly what he wants. I’m going to ask him to deliver it to Amiens.’

‘Why?’ Aimee gasped.

‘He won’t go to Amiens. He’ll take it to his friend Benedict and they will give it to some contact on the German side. Once he’s handed it over, and been paid, we’ll arrest them both.’

‘It’s still a risk,’ Colette said.

The officer shrugged. ‘I’ve got a good man following him secretly, don’t worry. Nothing can go wrong. Nothing.’

26 August 1918: The school, Bray

General Bruce stroked his moustache furiously. ‘I’d like to shoot Sergeant Grimm myself,’ he growled.

Captain Ellis stood calmly by the desk in the general’s office. ‘If we arrest Grimm then Benedict will just find someone else to steal our secrets. We need Grimm to lead us to Benedict.’

The general sighed. ‘Very well, send Silver Hand in.’

‘Yes, sir.’

The captain walked across the floor of the old school hall. He called through the door to the man with the silver hand. ‘The general wants to see you in his office at once, Sergeant Grimm.’

‘Yes, sir. Why, sir?’

‘Important job.’

They marched in step to the general’s office and found him sitting behind a desk. On the desk was the backpack that Captain Ellis had brought from the farm. Sergeant Grimm saluted smartly and stood stiffly with his eyes fixed on a map of the world on the wall, left over from when it had been a school.

‘Stand easy, Grimm,’ the general said. The sergeant’s shoulders drooped but he was still rigid and his eyes narrow with fear. ‘Now, I have an important task for you.’

‘Yes, sir.’

‘In this backpack you have a top-secret document,’ he said jabbing a finger at the front pocket. ‘It’s so secret we can’t risk sending it in the usual mail. It has to be taken by hand to Amiens so we can send it back to Britain. There, it will go to the prime minister.’

‘May I ask what the secret is, sir?’