The soldier stayed calm. ‘They are moving so fast they will leave their supplies far behind. By the end of the week they will have to stop and wait for food and bullets and hospitals to catch up. Especially the hospitals. We will pull our army back to Amiens. Then, when they are exhausted, we’ll strike. We’ll drive them all the way back to Germany.’

Aimee frowned. ‘What do you mean, especially the hospitals?’

Captain Ellis gave a small smile. ‘You’re a bright girl, Aimee. What I mean is we have reports coming in from our White Lady spies to the east. The enemy hospitals are filling up... and so are their burial grounds.’

‘Because you are shooting so many?’

‘No. Because there is disease spreading through the German army. They are falling sick in their thousands with influenza – or flu.’

‘Master DuPont, our teacher, had that last Christmas. He was off for three days and I had to teach the little ones,’ Aimee said with a shrug. ‘Then I was sick for a week.’

‘Then you are lucky. This is a new type of flu. It is deadly, but if you’ve had it – and then got better – you won’t catch it again.’

‘But it’s killing the Germans?’

‘When their soldiers are crammed into the motor-lorries that carry them forward they are spreading it. A few recover. Many are dead in three days. By the time the enemy reach Amiens they will be starving, they’ll have empty rifles and full hospital tents.’ He drank the red wine and rose to his feet. ‘Now I must get back to the school. General Bruce will arrive tomorrow morning and I want you, Colette, to be there.’

‘I can’t spy on the Germans from Aimee’s school,’ the woman laughed.

Captain Ellis put his hat back on his head. ‘No but you can help me spy on the British. The Germans have spies too. And one of them is in our general’s office, passing our secrets to the enemy. I want you to help me trap him.’

‘How?’ Colette Fletcher asked.

‘Act as a cleaner for the old school. Then you can go everywhere. The spy is too careful to let me see him at work. But he won’t pay any attention to a cleaner.’

‘Or a girl,’ Aimee said. ‘I’m coming too, Maman. I’m going to be a White Lady like you. Intus est hostis,’ she said.

‘The enemy is within the gates.’ Captain Ellis nodded. ‘He is indeed. You are welcome to join us in the hunt for him.’

And that was how Aimee set off on the search for the most dangerous man in France.

22 March 1918: East of Peronne