‘What?’ he said. ‘What is it?’ It was dark in the bedroom, darker than normal when he woke up. He looked at the alarm.

3.45.

It wasn’t time for him to wake up. He had another hour. More than an hour.

‘Alice,’ he said. ‘I’m sleeping.’

‘I was too,’ she said. ‘Jo’s been asleep for a while, for a change. I was on the couch, but something woke me up. You need to come and see it.’

‘Where is she now?’

‘Downstairs. She’s fine. Out like a light.’

He smiled. ‘That I do need to see.’

Alice didn’t smile back at him. ‘This isn’t a joke, Tom.’

Her tone was serious, and his adrenaline spiked, waking him up fully. He climbed out of bed and pulled on a T-shirt.

‘OK,’ he said. ‘I’m coming.’

He followed her downstairs and into the living room. Jo was asleep in her basket. There was a dent in the pillow on the couch where Alice had been lying.

‘What?’ he said. ‘I don’t see anything.’

‘On the table.’

There was an envelope lying on it, the address printed on a home printer. There was no stamp.

‘Holy shit,’ he said. ‘When did that arrive?’

‘Just now,’ she said. ‘I was sleeping and I was woken by the letter box snapping shut. I got up to take a look and this was there.’

‘Have you read it?’

She shook her head. ‘I don’t want to touch it. It’ll mess up the forensics. He was here, Tom. At our house, in the middle of the night.’

He glanced at Joanna. The serial killer who, one night ago, had tried to kill someone with a hammer, who already had at least four victims, had been at their house, twenty minutes ago.

Tom paused to consider what this meant. It was not only a letter. It was a signal: I’m getting closer.

He could have killed them all in their sleep.

‘This is crazy,’ he said. ‘Have you called the police? He could be out there right now. We need the cops here.’

‘I’ll do it now.’ Alice was pale, her expression serious. ‘And when they get here we can find out what it says.’

DI Wynne

Wynne was woken by her phone ringing. She looked at her alarm clock and sat up. It was just past four in the morning, and nothing good came from phone calls at that time.

Her sense of foreboding only increased when she saw it was Alice Sark. She had no reason to call Wynne that wasn’t related to the killings, at least not at this hour of the morning.

She answered the call.

‘Wynne.’

‘This is Alice Sark.’

‘Has something happened, Ms Sark?’

‘Sorry to call so early. I tried Nadia, but she didn’t pick up.’

‘Not a problem. What is it?’

‘Another letter,’ Alice Sark said.