'Maybe the car's broken down,' said Kemp. 'Maybe it wouldn't start. These cold mornings play hell with cheap batteries, you know.'

'They'll be here soon.'

On the far side of Hollowgate, shopkeepers were clearing the snow from the pavement in front of their shops, shovelling it into ugly heaps in the gutter. The beauty of snow vanished as soon as it was touched by the first footstep or the first spray of grit from a highways wagon. By daylight, it would be tarnished beyond recognition.

'I have to tell you I've got a delicate respiratory system,' said Kemp. 'Very susceptible to the cold and damp, it is. I might need medical attention if I'm kept outside in these conditions too long.'

'If you don't keep quiet, I'm going to get annoyed.'

'Bloody hell, what are you going to do? Shove a snowball down my neck?'

A pair of flashing blue lights lit up the front of the town hall in the market square, just past the High Street junction. Cooper and Kemp both looked towards the lights. It was an ambulance. The driver was struggling to make his way through the lines of crawling cars.

'That's clever,' said Kemp. 'Sending for the ambulance first, before you beat me up.'

'Shut up,' said Cooper.

'If you took the cuffs off for a bit, I could use my mobile to phone the missus. She could get the sledge out and hitch up the dogs. They're only corgis, but it'd be quicker than this performance.'

Behind them, somebody laughed. Cooper looked over his shoulder. Three men were standing in front of the window of the café, leaning on the plate glass, with their hands in the pockets of their anoraks and combat jackets. They wore heavy boots, a couple of them with steel toecaps, like the safety boots worn by builders in case they dropped bricks or scaffolding on their feet. Three pairs of eyes met Cooper's, with challenging stares. Four white males, aged between twenty-five and forty-five. Could be in possession of baseball bats or similar weapons. Approach with caution.

Finally, Cooper's radio crackled.

'Sorry, DC Cooper,' said the voice of the controller. 'Your response unit has been delayed by a gridlock situation on Hulley Road. They'll be with you as soon as possible, but they say it could be five minutes yet.'

One of the men leaning against the window began to form a snowball between his gloved fists, squeezing it into the shape of a hand grenade with short, hard slaps.

'Damn,' said Cooper.

Kemp turned his head and smiled. 'Do you reckon we could go back inside and have another cup of tea?' he said. 'Only I think it's starting to snow again. We could freeze to death out here.'

* * * *

By morning, Marie Tennent's body had stiffened into a foetal position and was covered in frost, like a supermarket chicken. Ice crystals had formed in the valves of her heart and in her blood vessels. Her fingers and toes and the exposed parts of her face had turned white and brittle from frostbite.