What’s that? What’s happening?’ shouted Mister Lewis, his ghostly hands pressed over his ears.

‘It’s the alarm!’ I cried. ‘Come on, we’ve got to get out of here.’

I reached in and grabbed the half stone from the shattered showcase, zipped it inside my jacket along with the other half. We ran between the other showcases, the two stones rattling together against my chest. When we reached the high window that we’d come through I stopped. There was a face at the broken window. And a voice I recognised. ‘Sergeant Johnson!’ I whispered, ducking under a showcase. Too late, he’d seen me.

‘You, boy,’ he shouted angrily, flashing his torch around. ‘What do you think you’re doing? I can see your legs. No point in hiding, the place is surrounded. You might as well give yourself up.’

‘Surrounded?’ muttered Mister Lewis. ‘Oh dear.’

‘Surrounded by him,’ I whispered. ‘There’s always only one Garda on night duty. I should know − my dad is a Garda and he’s on night duty every third week.’

Still, we’d have to risk going out through the museum door. But as we edged along the wall towards it, I was horrified to hear a key in the lock and bolts being pulled back. We were trapped! I frantically looked around the moonlit room for a hiding place. There was a Famine display of a life-size group of people sitting at a fake fire. I crept over and nicked a bit of sacking from a donkey cart and put it around my shoulders to look raggy. Then I sat beside a model of a boy whose paint-chipped hand was stretched towards the fire. I ducked lower when a beam from a torch flashed around. It was only a matter of moments before I’d be seen.

‘Who’s there?’ came an angry shout. I can never understand why people ask that question at a time like this. Like, someone who’s broken in is going to stand up and give his name, address and mobile number and say ‘take me away’? Anyway, I gasped when I recognised Mister Conway’s voice. I’d forgotten he lived upstairs. He’d heard us!

‘Do something,’ I hissed at Mister Lewis, who was sitting across from me, his tall hat askew, making him look like a worn-out scarecrow.

‘Do what?’ he hissed back.

‘Something ghostly. I’ll be in no end of trouble if I’m caught.’

If I did get caught, then I wouldn’t get to replace the two bits of stone, and Shane and Big Ella would be found dead in the morning. And me − found dead in a prison cell because Amergin, being a full spook, could just walk through the wall and clobber me. And my dad would be kicked out of the Gardaí and jailed for – I dunno – for having a criminal son, maybe. And Mum would have to leave the country in disgrace with a wig and a false passport. Such worries!

The beam of the torch was coming closer. I shut my eyes and held my breath as it stopped and then passed over me. Then there was a sound that startled me.

‘OOooo.’

I blinked. Mister Lewis was now standing beside a model of an old woman who was stirring something in a pot. His head was raised and he was uttering this ghastly wail. The beam of torchlight stopped, then focused on the display.

‘OoooooOO,’ went Mister Lewis, now in full cry.

‘Help!’ bawled Mister Conway. ‘Help!’ He stood frozen to the spot. With a clatter, the door burst open and Sergeant Johnson barged in.

‘Mister Conway!’ he exclaimed. ‘Have you caught the hooligans?’

‘Sergeant,’ said Mister Conway nervously. ‘There’s something …’

‘What, man, what? Are they armed and dangerous?’

‘Over there,’ whispered Mister Johnson. ‘That old woman …’

Sergeant Johnson shone his torch on the group. I sucked in my cheeks and hoped I looked hungry enough to be a Famine kid.

‘They’re models, man,’ he said, ‘just Famine models.’

‘She ooohhhed at me,’ whispered Mister Conway.

‘Huh? Don’t be ridiculous,’ began Sergeant Johnson.

Mister Lewis launched into another wail.

Sergeant Johnson jumped. ‘What the blazes?’ he shouted, clutching Mister Conway’s arm, even though Mister Conway was already hanging on to Sergeant Johnson’s collar.

‘OOOOooo,’ went Mister Lewis again. Then he changed position and slipped behind a hairy model of a donkey. ‘EEEEHAAAWW,’ he went.

Sergeant Johnson shone his torch in the direction of the donkey.

‘EEEHAAAWWW!’

‘See?’ shouted Mister Conway in panic. ‘It’s haunted!’

I could see the glee in Mister Lewis’s face as he wafted towards the two men. He turned and winked at me. He was visible to me and invisible to them. Neat trick. Then he shrieked louder than ever into their ears. That did it. The two men ran, tripping over one another. Mister Lewis followed them, screeching all the time. The door slammed and I could hear the clatter of panicky footsteps running into the street. Mister Lewis wafted back to me. He was laughing loudly as he wiped ghostly tears from his eyes with his sleeve and stuck back an eyebrow.

‘That was wonderful,’ he said. ‘Best fun I’ve ever had in my life. Eh, I mean death,’ he added. ‘I didn’t know I could shriek like that. Think of the fun I could have had all those years I’ve spent as a half-ghost. Come on, Milo. Let’s chase those two and maybe a few more passers-by for a laugh, eh?’

‘No way!’ I said. ‘Have you forgotten why we’re doing all this? Come on, we’ve got to get out of here before they come back with back-up.’

‘Yes, of course,’ said Mister Lewis, suddenly ghostly serious again. ‘It must be nearly midnight.’

That made me panic again. Luckily I hadn’t had dinner. I’d have thrown up right there on the museum floor – and if the cops didn’t get me, then forensics would. I’ve seen those guys on the telly – nailing a thug from just a splash of sneezed snot on a doorhandle.