Kensy drew her raincoat around her ears and huddled underneath the umbrella as she and Max hurried around the corner to Mrs Grigsby’s newsagency. London looked as if someone had thrown a wash of grey paint over it, although it wasn’t as cold as it had been.

‘Seriously, I almost died when I saw Magoo in the sitting room,’ Kensy said. ‘I thought he was there to talk to Fitz about something else I’ve messed up.’

‘I wish we could’ve gone with them,’ Max said. ‘I’d love to be testing some new gadgets.’

Kensy shot him a look. ‘Uh, I think we have enough to test for ourselves at the moment.’

‘Good point,’ Max conceded. He was carrying the ingredients in his small daypack as well as a lighter, a beaker, a set of measuring spoons, a bowl and a spare fire blanket filched from the pantry.

The twins left their umbrellas at the shop door and walked inside. The small television set behind the counter was blaring, but there was no sign of Derek.

‘Hello?’ Max called.

Derek’s head popped up like a meerkat over the top of the shelves in the second aisle. ‘Oh, hiya kids. I’m just restocking the tinned goods. We’ve ’ad a run on baked beans and tomato soup. Mostly from me,’ he said with a toothy smile. ‘What can I ’elp you wiv?’

‘Do you remember when we visited Mrs Brightside before Christmas?’ Max started. ‘Before she went on her holiday. You came into the house while we were there.’

Derek frowned and scratched his head through his beanie. ‘Yeah, I remember. Wish I didn’t, but that was ages ago.’

‘I think I might have lost my necklace in her house,’ Kensy piped up. ‘We haven’t been able to ask anyone until now because you’d all gone away.’ She was counting on the fact that Derek wouldn’t realise there had been a bit of time between them visiting Esme Brightside and the day the granny gang was rounded up by MI6.

‘What’s it got to do wiv me?’ Derek walked around to the counter and dumped the empty box on top.

‘We remembered that you were doing lots of jobs for Mrs Brightside before she went on holiday and we thought you might have a key to the house,’ Max added.

‘I’m not supposed to go there,’ Derek said gruffly. ‘It’s off limits.’

Kensy wrinkled her nose. ‘Why?’

‘It just is, that’s all.’ Derek picked up another box from behind the counter and tore it open.

Tears spilled down the girl’s cheeks. ‘Oh, Max, I can’t believe it’s lost forever,’ she said in a wobbly voice, and promptly burst into racking sobs. ‘I know it’s only a silly necklace, but it was from … from … And now she’s gone and my necklace is too.’

Max hugged Kensy tight and patted her on the back. ‘There, there, it’s okay. We still have our memories of her.’

Derek stood by awkwardly, watching them. ‘Blimey, you’re makin’ me feel like rubbish,’ he mumbled, looking as though he might burst into tears as well.

‘Have you got a key?’ Max whispered over his sister’s shoulder. ‘You don’t have to come with us. We could pop down and take a quick look around then bring it straight back.’

Derek’s eyes lit up. ‘You’re a genius, Max! You should get a tattoo, same as mine.’

Max bit back a smile as Derek walked out into the room behind the shop.

‘Ever thought about a career on the stage, Kens?’ Max breathed.

His sister grinned. ‘You weren’t too bad yourself.’

Derek returned a minute later with a silver key on a ring. ‘’Ere you go, kids. Just make sure that you bring it straight back,’ he said, dropping it into Max’s outstretched hand.

The girl attempted a smile. ‘Thank you, Derek, you’re an angel,’ she sighed, adding a final sniffle for effect.

Without a backwards glance, the twins hurried out of the shop and into the rain, snatching up their umbrellas on the way.