I go to put the book back but then notice the lid of the box file has slid off. I lift it up. Inside are old photographs of Granddad and Grandma. I pick up a bundle of them and flick through – Granddad and Grandma on a bridge. Granddad and Grandma sitting together on a tram. Granddad and Grandma standing by a huge wall covered in graffiti with soldiers guarding it. Someone who looks like a young version of Granddad, standing next to a small boy in a hall, surrounded by lots of chessboards on tables.

I drop them back in the box and pick up some yellow cards. There’s a lot of German writing and even if I could read German I still don’t think I could understand it because it looks like it’s written in code: ‘Vorgart-MFX 8628/76’. In the middle of it is Granddad’s name: ‘Francke Schopp’ and then his birthday: ‘21/12/1943’. On another card someone has written ‘Ministerium für Staatssicherheit’ and there’s a picture of a red hand holding a rifle. All the cards have the same name at the bottom: ‘Commander Steiner’.

‘Have you found it?’ Granddad shouts up the stairs and makes me jump. ‘I’m sure I put it on the dressing table.’

I quickly drop the cards back in the box.

‘You did, Granddad,’ I yell back. ‘I got it, now I’m just going to the toilet.’

I close the wardrobe door slowly and pick up the knight.

X + Y = Spy!

The enemy are retreating. Our machine-gun fire has scared them away – we can hear the rumble of tanks as they flee back to base.

It’s Friday evening and I’m sitting on the platform. Jake’s leaning against the tree trunk, chewing gum.

‘So say it again?’ he says. ‘You found cards . . .’

‘Yes. They were a bit like his appointment cards for hospital, only in German.’

‘And you found pictures of soldiers.’

‘Yes, standing by a wall. I don’t know if it was the same one but he told me about a massive wall in Berlin with barbed wire on top and people on one side of it watched the other side like spies. I wanted to know more, but that’s all he’d tell me.’

‘Mmm . . . weird.’ Jake looks across the grass towards Granddad’s house. ‘It’s strange that he never talks about his past, and how he keeps his curtains closed all the time.’

‘Jake,’ I sigh. ‘Please don’t go on about my granddad again.’

‘I’m not.’ He gives me his I’m innocent look. ‘I’m just saying it’s weird. Like the way he doesn’t talk to anyone and how he’s got into your head so all you talk about is chess. It’s like he’s brainwashing you.’

‘Don’t be daft,’ I say. ‘He’s just teaching me.’