There were no further markings on the next three pages, but Paul’s heart leaped when the blue light exposed an entire page aglow with his father’s handwriting. Names, phone numbers, dates, times and places of meetings. However, no mention of Henderson.

Over the next few pages Paul discovered more notes glowing under the blue light, but none of them seemed to relate to Henderson and he grew increasingly nervous as he got close to the end of the book.

Finally, just a few pages from the end, he found a quickly scrawled note: Henderson C. home 34451 Embassy 34200. Paul felt a rush of excitement as he burst out from under the bedcovers and grabbed something to write down the numbers on before he forgot them.

Once they were safely transcribed, he bolted downstairs and waved the piece of paper under Rosie’s nose as she dried a roasting tin with a dish cloth.

‘Are you joking?’ Rosie grinned as she wrapped her wet hands around her brother’s back and gave him a hug. ‘How did you find that? I’ll ask Father Doran where the nearest phone is. We can call him straight away.’

‘Father Doran,’ Paul shouted, as he ran out of the kitchen and into the living room. ‘We’ve got a number for Mr Henderson.’

The elderly priest had cleared the dining table and set out playing cards and wine glasses for his friends.

‘You have?’ he smiled.

‘I found a torch,’ Paul explained. ‘It shows up the hidden writing in my dad’s pocket book.’

‘Ahhh,’ the priest said, wagging his finger knowingly. ‘Ultra-violet light. I believe the Vatican used a similar technique for passing messages during the Great War. Well, that’s marvellous – assuming that this Henderson is still in Paris.’

‘And that the phone lines are working,’ Rosie added. ‘Paris is behind German lines now. I’ve got no idea whether we’ll be able to get through. We need a phone, Father. Do you know anyone around here who has one?’

‘I’ve never used one myself,’ the priest said. ‘But there’s a vineyard about three kilometres down towards the village. The owner is a widow I’ve known for many years. I’m sure she’ll let you use her phone, if it’s working.’

‘Great,’ Paul said. ‘We’ll head up there now.’

CHAPTER TWENTY-TWO

‘Got him,’ the junior officer announced triumphantly, as he dragged Marc from behind the chair. Before the boy knew it he’d been shoved backwards into the armchair and the Oberst loomed over him.

‘What is your name?’ the black-uniformed Oberst shouted, switching to French that was about as competent as Marc’s German.

‘David Henri,’ Marc lied.

‘Do you speak German?’

Marc nodded. ‘A little bit.’

‘If you understood our conversation, you’ll know what I want to hear.’