They would both see the beginning of the Ripper’s killing spree but Arkwright would be retired long before the end of it. Donald Neilson, the Black Panther from Bradford, hadn’t been captured yet and Harold Shipman had probably already started killing patients unlucky enough to be under his care in Pontefract General Infirmary. West Yorkshire in 1975, awash with serial killers.

Tracy Waterhouse was still wet behind the ears, although she wouldn’t admit to it. Ken Arkwright had seen more than most but remained avuncular and sanguine, a good copper for a green girl to be beneath the wing of. There were bad apples in the barrel – the dark cloud of David Oluwale’s death still cast a long shadow on police in the West Riding, but Arkwright wasn’t under it. He could be violent when necessary, sometimes when not, but he didn’t discriminate on the grounds of colour when it came to reward and punishment. And women were often slappers and scrubbers but he’d helped out a few street girls with fags and cash, and he loved his wife and daughters.

Despite pleas from her teachers to stay on and ‘make something of herself’, Tracy had left school at fifteen to do a shorthand and typing course and went straight into Montague Burton’s offices as a junior, eager to get on with her adult life. ‘You’re a bright girl,’ the man in personnel said, offering her a cigarette. ‘You could go far. You never know, PA to the MD one day.’ She didn’t know what ‘MD’ meant. Wasn’t too sure about ‘PA’ either. The man’s eyes were all over her.

Sixteen, never been kissed by a boy, never drunk wine, not even Blue Nun. Never eaten an avocado or seen an aubergine, never been on an aeroplane. It was different in those days.

She bought a tweed maxi coat from Etam and a new umbrella. Ready for anything. Or as ready as she would ever be. Two years later she was in the police. Nothing could have prepared her for that. Bye Bye,Baby.

Tracy was worried that she might never leave home. She spent her nights in front of the television with her mother while her father drank – modestly – in the local Conservative club. Together, Tracy and her mother, Dorothy, watched The Dick Emery Show or Steptoe and Son or Mike Yarwood doing an impression of Steptoe and his son. Or Edward Heath, his shoulders heaving up and down. Must have been a sad day for Mike Yarwood when Margaret Thatcher took over the leadership. Sad day for everyone. Tracy had never understood the attraction of impressionists.

Her stomach rumbled like a train. She’d been on the cottage cheese and grapefruit diet for a week. Wondered if you could starve to death while you were still overweight.

‘Jesus H. Christ,’ Arkwright gasped, bending over and resting his hands on his knees when they finally achieved the fifteenth floor. ‘I used to be a rugby wing forward, believe it or not.’

‘Ay, well, you’re just an old, fat bloke now,’ Tracy said. ‘What number?’

‘Twenty-five. It’s at the end.’

A neighbour had phoned in anonymously about a bad smell (‘a right stink’) coming from the flat.

‘Dead rats, probably,’ Arkwright said. ‘Or a cat. Remember those two dogs in that house in Chapeltown? Oh no, before your time, lass.’

‘I heard about it. Bloke went off and left them without any food. They ate each other in the end.’

‘They didn’t eat each other,’ Arkwright said. ‘One of them ate the other one.’

‘You’re a bloody pedant, Arkwright.’

‘A what? Cheeky so-and-so. Ey up, here we go. Fuck a duck, Trace, you can smell it from here.’

Tracy Waterhouse pressed her thumb on the doorbell and kept it there. Glanced down at her ugly police-issue regulation black lace-ups and wiggled her toes inside her ugly police-issue regulation black tights. Her big toe had gone right through the hole in the tights now and a ladder was climbing up towards one of her big footballer’s knees. ‘It’ll be some old bloke who’s been lying here for weeks,’ she said. ‘I bloody hate them.’

‘I hate train jumpers.’

‘Dead kiddies.’

‘Yeah. They’re the worst,’ Arkwright agreed. Dead children were trumps, every time.

Tracy took her thumb off the doorbell and tried turning the door handle. Locked. ‘Ah, Jesus, Arkwright, it’s humming in there. Something that’s not about to get up and walk away, that’s for sure.’

Arkwright banged on the door and shouted, ‘Hello, it’s the police here, is anyone in there? Shit, Tracy, can you hear that?’

‘Flies?’

Ken Arkwright bent down and looked through the letterbox. ‘Oh, Christ—’ He recoiled from the letterbox so quickly that Tracy’s first thought was that someone had squirted something into his eyes. It had happened to a sergeant a few weeks ago, a nutter with a Squeezy washing-up bottle full of bleach. It had put everyone off looking through letterboxes. Arkwright, however, immediately squatted down and pushed open the letterbox again and started talking soothingly, the way you would to a nervy dog. ‘It’s OK, it’s OK, everything’s OK now. Is Mummy there? Or your daddy? We’re going to help you. It’s OK.’ He stood and got ready to shoulder the door. Pawed the ground, blew air out of his mouth and said to Tracy, ‘Prepare yourself, lass, it’s not going to be pretty.’

Six months ago

The suburban outskirts of Munich on a cold afternoon. Large, lazy flakes of snow fluttering down like white confetti, falling on the bonnet of their anonymous-looking German-made car.

‘Nice house,’ Steve said. He was a cocky little sod who talked too much. It was doubtful that Steve was his real name. ‘Big house,’ he added.

‘Yeah, nice big house,’ he agreed, more to shut Steve up than anything else. Nice and big and surrounded, unfortunately, by other nice big houses, on the kind of street that had vigilant neighbours and burglar alarms dotted like bright carbuncles on the walls. A couple of the very nicest, biggest houses had security gates and cameras attached to their walls.

The first time you recce, the second time you pay attention to detail, the third time you do the job. This was the third time. ‘Bit Germanic for my liking, of course,’ Steve said, as if the entire portfolio of European real estate was at his disposal.

‘Maybe that’s something to do with the fact that we’re in Germany,’ he said.

Steve said, ‘I’ve got nothing against the Germans. Had a couple in the Deuxième. Good lads. Good beer,’ he added after several seconds’ contemplation. ‘Good sausages too.’

Steve said he’d been in the Paras, came out and found he couldn’t handle civilian life, joined the French Foreign Legion. You think you’re hard and then you find out what hard really means.

Right. How many times had he heard that? He’d met a few guys from the legion in his time – ex-military guys escaping the flatline of civilian life, deserters from divorces and paternity suits, fugitives from boredom. All of them were running from something, none of them quite the outlaws they imagined themselves to be. Certainly not Steve. This was the first time they’d done a job together. The guy was a bit of a gung-ho wanker but he was OK, he paid attention. He didn’t smoke in the car, he didn’t want to listen to crap radio stations.

Some of these places reminded him of gingerbread houses, right down to the icing-sugar snow that rimmed their roofs and gutters. He had seen a gingerbread house for sale in the Christkindl market where they had spent the previous evening, strolling around the Marienplatz, drinking Glühwein out of Christmas mugs, for all the world like regular tourists. They’d had to pay a deposit on the mugs and on that basis he had taken his back to the Platzl, where they were staying. A present for his daughter Marlee when he got home, even though she would probably turn her nose up at it, or, worse, thank him indifferently and never look at it again.