I nodded. ‘I hear him too,’ I said.

‘I think he misses his old home.’

‘No,’ I said. ‘He misses his mother’s heartbeat. But there’s a trick for young dogs that miss their mothers. I’ll show you.’

I found an old alarm clock and slipped it under the blanket in the dog’s basket.

‘He’ll think it’s his old mum dog,’ I said. ‘He’ll hear the tick-tock of the clock and he’ll think it’s her heartbeat.’

Scout looked so doubtful that the idea suddenly seemed ridiculous to me.

But it worked.

That night I lay awake until just before dawn, turning my pillow over until the meat market fell silent and the light in the room was milky grey. Stan did not whimper once.

Chapter 8

8

THE BLACK MUSEUM of Scotland Yard is not a museum at all. It is not open to the public and its contents are guarded behind heavily locked doors. Officially, it is not even called the Black Museum. After complaints from officers working in areas with large ethnic minorities, it was renamed the Metropolitan Police Crime Museum, an enforced change that ensured we would always and forever call it the Black Museum.

As I had told PC Greene, the Black Museum is a teaching aide. That was why it was established in the Victorian era, that was why it still existed – to save the lives of policemen by educating them in the criminal’s tools of the trade.

And that was why DCI Mallory and I went to the Black Museum. I had spent a full day on HOLMES2, slogging through just one item on the MLOE checklist – identifying modus operandi suspects, murderers who killed by cutting throats and who were neither dead nor in prison. It was a long, frustrating day of too many dead ends and too much caffeine.

So when the day’s light was fading, we went looking for a murder weapon.

DCI Mallory and I stood outside Room 101 in New Scotland Yard. He was grinning broadly.

‘Room 101,’ he chuckled. ‘It’s almost too perfect, isn’t it?’

I must have looked baffled.

‘Room 101,’ he repeated, frowning with mild disappointment. ‘The torture chamber in the Ministry of Love. George Orwell? 1984?’

My brain scrambled to catch up. I had read 1984 when I was a kid. Somebody made me. ‘Where the rats are,’ I said. ‘The rats in the cage that get strapped to Winston’s face.’

‘Room 101 is the place of your worst nightmare,’ Mallory said. ‘It’s the room that contains the worst thing in the world. O’Brien tells Winston that we all know what is waiting for us inside.’

Mallory knocked on the door and a voice told us to come in.