My cell beeps, but when I pull it out expecting yet another snarky message from Mother, I see it switching itself off. The battery has given up – I’ve never thought to charge it.

The chief walks into the room, his face all grey stubble and greyer skin. If we don’t catch the Watcher soon, he may well die of exhaustion. He needs twelve hours’ sleep, a hearty meal and then another half day in bed.

Cuthbert takes the opportunity to head for the bathroom. Since being detailed as my bodyguard he’s never been more than six feet away from me.

‘Got anything yet?’

‘Not a thing. What about your end?’

‘Zilch. We’ve traced as many of the people at the nature reserve as we can, but none of them saw anything.’

‘What about the last victim? She was supposed to be meeting her date at seven, wasn’t she?’

‘We’ve spoken to him. He was at work all day and then his roommate vouches for him from the time he left work until he went to meet her.’ He kneads his temples. ‘After being stood up he sank a couple of beers and went home. Her cell had four missed calls and a succinct message from him, but his whereabouts are vouched for from leaving work until he went to bed.’

I know it isn’t the date, but he still has to be checked out. There’s something nagging me about the last kill, but I can’t figure out what.

The timeline between Norm Sortwell finding Ian Yarwood’s body and his cousin dying is so short it means the Watcher is escalating his kills with increasing rapidity.

There were less than eight hours between the two events and it doesn’t seem credible someone could have learned who Norm was, traced his family, executed a kill then dumped a body in such a short time frame.

If I didn’t know it was impossible, I’d start to think Norm was supposed to find Yarwood’s body.

Alfonse bursts into the office as Cuthbert is closing the door behind him. Cuthbert’s hand flies into his jacket and emerges with a gun. He’s halfway towards aiming it when he recognises Alfonse.

‘I think I may have found him.’

‘Who?’ Three voices speak as one.

‘When I started looking into the first…’

The chief beats me to the interruption. ‘Tell us the who first. Then you can explain how you’ve found him.’

‘It’s Norm Sortwell.’

There’s a stunned silence until I wave a hand at Alfonse. ‘Why do you think it’s him?’ It’s tough to believe when his cousin is the latest victim.

‘As I was saying. When I started to look into Ingerson’s family, I found out his wife used to be a nurse. A few weeks after he was killed she was fired.’

‘Why?’

‘The clinic she worked at was sued for infecting a patient with HIV from a dirty needle. She was the nurse who had used the needle. The case was settled out of court by the insurers.’ Alfonse gives a grim smile of self-congratulation. ‘The patient who was infected had already died by the time this all happened. Her name was Melanie and she was married to Norm Sortwell. The same Norm Sortwell who found Ian Yarwood’s body.’

The chief shakes his head. ‘Coincidence. His cousin was killed.’

‘Here, I’ve printed out everything I found so you can check it for yourselves.’ Alfonse pulls a sheaf of papers from his briefcase.

He sits down at a desk and starts to boot up his laptop while we absorb what he’s told us.

I let the chief and Cuthbert read the printouts Alfonse has supplied. I trust his judgement, but I need to work it through my own mind before fully accepting his accusation.

Starting at the beginning I put together a mental chain of events. Faith Ingerson’s stupidity or laziness caused Norm’s wife to catch a deadly virus. He’d sued the clinic after Melanie’s death. The settlement he’d received wasn’t enough for him though, he had wanted to see her punished.

After losing his own spouse, he must have decided it was fitting for her to lose hers. Where his selection process had come from or why he’d carried on killing is still unknown but there is always the possibility he’d got a taste for it or had suffered a mental breakdown of some kind after his wife’s death.

‘Did you have chance to look into him?’

‘Yeah. It’s not pretty. He was in the Marines for years. Done all the usual tours, Helmand, Baghdad and so on. I also looked at his medical records. He’s now got full blown AIDS.’

I think of Norm’s appearance. The gaunt face, depleted body tissue and the belt showing used holes where he’d lost weight.

He is dying and knows it. Perhaps he wants to go out with a bang or just get even with the world for the hand he’s been dealt. Maybe the twin blows of losing his wife and contracting a death sentence saw his mind disintegrate.

The chief’s voice is laced with doubt as he turns on Alfonse. ‘Hang on a minute. Sortwell was under police guard from the moment he found the body until his cousin was discovered. There’s no way he could have killed her.’

Alfonse’s face is filled with dismay at having his logic unpicked.

‘I think you’re wrong, Chief.’ I ignore his sneer and press on. ‘I reckon the cousin was killed and dumped before he called in the body he supposedly found. He’s using us to provide the alibi you’ve just stated. Have you had a time of death for her yet?’

He doesn’t speak. Instead he reaches for the nearest telephone.

Cuthbert has a cell to his ear and I can hear him requesting someone joins us. I guess it’s Doenig.

Since Alfonse arrived, a new energy has filled the room. It’s banished the odours of defeat and helplessness and is energising tired limbs with a sense of purpose.

The more I think about it, the more I believe Norm Sortwell is the Watcher. As a former Marine he’ll have the necessary skills to have made the kills. Plus, he’d be able to get close to his cousin to kill her. While we still don’t have a cause of death, there are too many inconsistencies about her death fitting into the narrative of someone else killing her so soon after Yarwood’s body was discovered.

First there was the missed date. She’d posted about it on Facebook and there were clothes laid out ready on her bed. Judging by the length of the skirt and the fancy underwear, it wasn’t a date she planned to miss.

Second, if she’d changed her mind about the date why hadn’t she called or messaged the guy. She was a professional woman in her forties, not some immature teen. With the ease of cell messages as a way of communication, being stood up is becoming a thing of the past.

Third, if she had decided to miss the date, why weren’t the clothes put away? Where was she for the five and a half hours between leaving work and Norm finding Yarwood?

Fourth, no woman I’ve met in the last five years would go anywhere without her cell and purse. Both of which Josie had left behind if she’d left the house of her own volition.

Everything I can think of suggests Josie had been killed before she was due to go on the date. Therefore, the Watcher had got to her between her arriving home at five-thirty and getting dressed for the date at say six-thirty. This left a one-hour window.

Remembering how long Sharon used to spend in the bathroom, I know an hour isn’t a lot of time for a woman getting ready for a date. Especially the kind of date the lacy underwear on the bed suggested.

Josie wouldn’t have wanted anyone to disrupt her. All but close family members would have been shunned or rescheduled. Norm was family and would be allowed in, even if only for a few minutes. A trained Marine wouldn’t need more than seconds to kill a defenceless woman.

The chief hangs up his call as Doenig enters the room. His expression is unchanged apart from a slight lifting of the eyebrows.

‘You’re right, Boulder. Dr Green says the time of death was around seven o’clock last night give or take an hour or two.’

As the chief brings Doenig up to speed, I ask Alfonse what he’s working on.