I looked at Lesley, who shrugged. ‘No sir,’ I said.

‘So he could have been in Los Angeles when the murder was committed.’

‘We thought we’d ask him, sir,’ I said.

Toby started barking, not his usual annoying yap but proper furious barks. For a moment I thought I felt something, a wave of emotion like the excitement of being in a crowd at a football match when a goal is scored.

Nightingale’s head snapped round to look at the Coopertowns’ house.

We heard a window break and a woman screaming.

‘Constable, wait!’ shouted Nightingale, but Lesley was already through the gate and into the garden. Then she stopped so suddenly that Nightingale and I nearly piled into her back. She was staring at something on the lawn.

‘Jesus Christ, no,’ she whispered.

I looked. My brain kept trying to slide away from the idea that someone had thrown a baby from a first-floor window. Tried to convince me that what I was seeing was a scrap of cloth or a doll. But it wasn’t.

‘Call an ambulance,’ said Nightingale and ran up the steps. I grabbed my phone as Lesley stumbled over to the baby and fell to her knees. I saw her turn the little body over and feel for a pulse. I gave the emergency code and the address on automatic. Lesley bent over and started mouth-to-mouth resuscitation, her mouth covering the baby’s mouth and nose in the prescribed manner.

‘Grant, get in here,’ called Nightingale. His voice was steady, businesslike. It got me moving up the steps and onto the porch. Nightingale must have kicked the front door right off its hinges because I had to run right over it to get into the hall. We had to stop to work out where the fuck the noise was coming from.

The woman screamed again – upstairs. There was a thumping sound like somebody beating a carpet. A voice, I thought it might be a man’s but very high-pitched, was screaming: ‘Have you got a headache now?’

I don’t even remember the stairs. Suddenly I was on the landing with Nightingale in front of me. I saw August Coopertown lying face down at the far end of the landing, one arm thrust through a gap in the banisters. Her hair was wet with blood and a pool was growing under her cheek. A man stood over her holding a wooden baton at least a metre and a half in length. He was panting hard.

Nightingale didn’t hesitate. He bulled forward, shoulder down, obviously planning to take the man down in a rugby tackle. I charged, too, thinking I’d go high to pin the man’s arms after he’d gone down. But the man whirled around and casually backhanded Nightingale with enough force to slam him into the banisters.