“Wait-show me your left hand.”

Reluctantly, the boy opened his fist and raised it. There, a tiny blue curlicue stained his palm.

“What is that?” Longbright held his wrist and examined the mark. A fragment of mirror lettering revealed the familiar spikes of Finch’s strange handwriting.

“You had his notes after all. You crumpled them up with your sweaty palm and transferred the still-wet ink from his fountain pen.”

Longbright rose and walked behind Mills, gently teasing her fingers down the collar of his sweatshirt.

“Hey!” Mills attempted to squirm away, but the DS was too quick for him. She extracted the cheap gold chain from under his shirt and hauled him back to the chair.

“I think you’d better sit down and tell us what you did with the papers you took,” she said, permitting herself a smile. “Then you can explain why you stole jewellery from a dead girl.”

“I spy with my little eye, something beginning with S.” Bryant looked out through the frosted windscreen with cheery wide eyes. His white fringe was standing on end, an effect of the lowering temperature. He looked like Jack Frost’s grandfather.

“I’m not even going to dignify that with an answer.” May sighed.

“Can’t we call them again?”

“You said yourself that they need to stand on their own feet. We won’t always be around, you know.”

“I certainly won’t be around for much longer if you continue to ration the heater.” He tapped ineffectually at the radio. “The bulldozers should have been here by now. All they keep saying is that the driving winds are keeping rescuers at bay.”

“This isn’t the only road blocked. Presumably it’s affecting every major route for miles around, and there’s more snow on the way. We’re going to be here overnight, so we should try to get some sleep.”

The props in the back of the van were wrapped in old blankets, bubble wrap and plastic bags to protect their edges. Keeping warm would be easy enough, but Bryant worried how the passengers in other vehicles were faring. He knew they should really go and check, but stepping outside now would place them both in danger. Neither man was equipped to face subzero temperatures.

They put the heater back on, and were dozing in its desiccating warmth when the fist at their window made them both start. All John May could see was a pair of alarmed brown eyes peering through the furry tunnel of a green snow hood. He rolled down the glass.

“Thank God,” said the man, “nobody else will open their windows-there’s been a terrible-‘

“Wait,” May shouted, “I can’t hear you. Go around the back.” He climbed out of the van and plodded around it, cracking ice from the frozen rear door handle. The man in the green parka clambered up and shook down his hood. He was young, Chinese, frightened. If he noticed that he had been seated next to a gigantic gold-painted statue of Ganesh the Elephant God, he chose not to comment. “I’m in the Honda Civic back there. My engine stalled and the heater died,” he explained. “I needed to keep warm but didn’t have any other clothes in the car with me. There was a truck behind me-I could vaguely see the driver in my rearview mirror-so I thought I’d ask him if I could sit in his cabin. The truck’s side windows were covered in snow and I couldn’t see in, so I tried the driver’s door. I’m sorry-‘ The man fought down a wave of panic. ”I need to call the police-my mobile has no battery left, I just needed to tell someone-’

“It’s all right, you’ve found yourself a pair of police officers,” said May.

“He’s dead, lying across the seat; someone’s cut a hole in his throat. It must have only just happened, because blood is still pouring out. I tried to stop it, but didn’t know what to do.” He held up a crimson left hand.

“Was he alone? Did you see a passenger?”

“No, but the door was swinging open. It hadn’t been properly closed. I must have only just missed him.”

“It’s probably a good thing that you did. You’d better stay here while I go and look.”

“I’m coming with you,” Bryant called from his base deep within the passenger seat.

“It’s freezing out there, Arthur. You’re better off staying in here.”

“Don’t be ridiculous. My blood is so thin I’m virtually reptilian. I haven’t felt anything in my extremities since I landed on my arse in the Princess Diana Memorial Fountain. Besides, you need my help. You’re not as steady on your pins as you once were.”

“I resent that,” muttered May. “Come on then, just for a minute, but do your coat up properly.”

With the wind trying to whip the handle from his grasp, May had trouble closing the van door until their witness reached out to help him pull it shut. The detectives padded back along the column of stranded cars to the grocery truck, but any footprints that might have been left around it had already been obliterated by the gale. The snow coated their ears and eyes in feathered clumps. The mere act of breathing stung their noses and throats. The sky, the hills, the wind itself was white. The moorlands had been transformed into a blanched ice-desert, the trees bent low in frozen peninsulas of frost. May needed gloves and proper boots. His leather town shoes had become soaked in seconds. As he fumbled with the driver’s door, he realised he had already lost all sensation in his hands.

“Oh, let me do it,” said Bryant. “There.” The door came open in a spray of crystal shards.

The driver’s body was splayed across the seat on its back with one arm draped across a distended stomach, the mouth agape, as in the throes of a nightmare. The interior of the cabin had been darkened by snow building up across the windscreen, but there was enough light to reveal the hole beneath the driver’s chin. In the freezing exposure of the cabin, blood had quickly coagulated and darkened across the upholstery.

“Penknife or scissor wound,” said Bryant. “Interesting.”

The dead man appeared to be in his mid-forties but was probably younger. He wore the blue overalls provided by his company. A badge read Bentick’s-We Deliver. ‘Dreadful skin, looks like he hasn’t had a drink of water in years,“ sniffed Bryant. ”Subsisted on a diet of cigarettes, coffee and bad motorway food.“

May had forgotten to pack the Valiant, his trusted old cinema torch, but he was enough of a pessimist to still carry a pencil flashlight in his jacket. He shone it into the pale wash of light and picked up blood spots on the steering wheel, a streak across the base of the windscreen, a still-wet smear on the dashboard. “No struggle here,” he told Bryant, “just surprise and collapse. He was attacked by someone who posed no threat. Someone he probably thought was a friend.”

“The passenger. A hitchhiker, you think? He fled the scene pretty quickly. Blood on the passenger door handle. He won’t last long out there in the blizzard.”

“Not unless he’s climbed into one of the other stranded vehicles. Someone else could be in danger. We need to get a description of him somehow. I can’t get much from the crime scene in these conditions.”

Bryant looked up at the windscreen. “I don’t understand.

This window is snowed over. How could your witness have seen the driver through the glass?“

“You don’t think that’s our man?” asked May. “Why on earth would he have come to us?”

“I don’t think he faked looking that terrified, John. We can’t trust what we see. Snow and wind can do anything to this landscape.”

“Okay, let’s get back to the van. You’re starting to turn blue.”

They trudged back through the white valley of stranded cars. The rear door of the van stood wide, and without its heater running the Bedford had started to ice solid. Their witness was nowhere to be found. May took his mobile from the dashboard and got connected to the Plymouth constabulary.