Insch ordered the mobile incident room brought down to Duthie Park. It was little more than a glorified caravan, a grubby white rectangular box with 'Grampian Police' written on the outside and a small, sectioned-off interview room inside. The rest of the space was taken up by a couple of desks, a microwave and a kettle. The latter was going full time, filling the claustrophobic room with belching clouds of white steam.

The search teams weren't having any success and the snow was hungrily eating up any evidence there was, the wind sweeping it across the park, filling every indentation, making everything uniformly white and rounded.

Logan sat at the desk nearest the door, getting a chill in his kidneys every time the thing was opened and another frozen body staggered in, stomped their feet clean of snow on the carpet and looked hungrily at the kettle. He was hammering away at a laptop, a list of all known sex offenders in the city scrolling past his eyes. If they were lucky they'd find someone living near enough to the park to make it an attractive hunting ground. It was a big 'if: the other two bodies had been found on the other side of the city. One on the banks of the Don, the other in Seaton Park. Both a stone's throw away from the river that cut through the northernmost third of the city.

'Maybe we're looking for a different man?' he said aloud, causing Insch to look up from his pile of reports.

'Don't even think about it! One sick bastard abducting children is enough!'

Logan shivered as the door banged open again and a red-nosed WPC stumbled in from the snow. While she begged a cup of Bovril, Logan went back to his list of perverts, rapists and paedophiles. There were two registered in Ferryhill, the area directly butting onto Duthie Park, but they were both down for raping women in their mid-twenties. They weren't likely to kidnap, kill and abuse four-year-old boys, but Logan sent a couple of patrol cars anyway. Just to be sure.

More and more negative reports were coming in from the search teams. Insch had abandoned any hope of finding Jamie McCreath in the Winter Gardens and had sent everyone off to comb the park instead.

Logan's eyes drifted across a familiar name and he stopped. Douglas MacDuff: Desperate Doug. He wasn't a registered sex offender, but he was on the list as a suspect for some rapes twenty-odd years ago. The rest of the names were only recognizable because Logan had been through this exercise just last week, looking for suspects who might have taken little David Reid, or Peter Lumley.

A headache was beginning to nip him between the eyes. That was what he got for sitting here in a perpetual draught, hunched over this damn laptop. Achieving nothing. It was hard to believe this was only Wednesday. He'd been back on the job for eleven days now. Eleven days without a break. So much for the working time directive. Grunting, he rubbed the bridge of his nose, trying to get the growing pain to shift.

When he opened his eyes again he was staring at another familiar name: Martin Strichen, 25 Howesbank Avenue. The man who could fell slimy lawyer bastards with a single blow. And Slippery Sandy had the brass neck to say that Cleaver going free was the police's fault…A small smile flickered onto Logan's face as he played the moment of impact in his head. Bang. Right on the nose.

Insch looked up from the shivering WPC's report. 'What's so damn funny?' he asked Logan, his expression making it clear that there was nothing to laugh about.

'Sorry, sir, I was just remembering when Slippery Sandy got his nose broken.'

The annoyed look slid off Insch's face. Maybe there was something to smile at after all. 'Bang!' he said, slapping a fat fist into the other palm. 'I've got it on video now. Going to get someone to cut it to disk so I can use it as a screensaver on the computer. Bang…'

Logan grinned and looked back down at the laptop. There were plenty more names on the list to go through. Ten minutes later he was standing in front of the large-scale map of Aberdeen laminated and mounted on the mobile incident room's far wall. They'd marked it up in red and blue pen, just like the map back at Force HQ: red for where the kids had been abducted, blue for where the bodies had been found. Only now there was a red circle over Duthie Park as well.

'Well?' Insch demanded at last, when Logan had been standing there, motionless, for five minutes.

'Hmm? Oh, I was wondering about the parks connection. We found Peter Lumley in Seaton Park, Jamie McCreath was snatched from Duthie Park…' Logan picked up a blue marker pen and tapped it against his teeth.

'And?' There wasn't a lot of patience in Insch's voice.

'David Reid doesn't fit.'

With a growl of low menace, Insch asked Logan what the hell he was talking about.

'Well,' Logan prodded the map with the pen, 'David Reid was snatched from the amusement arcades down at the beach and dumped by the river in the Bridge of Don. No parks.'

'We've been through all this!' Insch glowered.

'Yes, but back then we only had the two disappearances. Maybe not enough to see a pattern.'

The door battered open, bringing with it a howling gale and WPC Watson. She clattered it shut again and banged her feet, making a miniature snowstorm on the linoleum. 'God, it's freezing out there!' she said, her nose like a cherry, her cheeks like apples, her lips like two thin strips of purple liver.

Insch let his glare leave Logan, roam towards Watson and return. Oblivious to the inspector's gaze, she wrapped her gloved hands around the kettle, stealing as much heat from it as she could.

'There has to be something,' said Logan, staring at the map, the blue marker pen clicking off his top teeth again, 'something we're not seeing. A reason this kid is different?' He stopped. 'Or maybe he isn't different at all…all these places have something in common…'

Hope shone in Insch's eyes. 'What?'

Logan shrugged. 'No idea. I know there's something, but I can't put my finger on it.'

And that was when Detective Inspector Insch finally lost his temper. He slammed his fist down on top of the desk, making the piles of paper dance and demanded to know what the blue fucking hell Logan thought he was playing at? There was a child missing out there and all he could do was play silly fucking games? His face was glowing beetroot-red, spittle arcing in the incident room's fluorescent lights as he tore a strip off of the first target to have presented itself since the McCreath child had gone missing.

'Er…' said Watson when Insch paused for breath.

The inspector snapped such a baleful look in her direction that she actually took a step backwards, holding the hot kettle to her chest like a shield. 'What?' he roared.

'They're all maintained by the council?' she said, getting the words out as quickly as possible.

Logan turned back to the map. She was right. Every single place he'd marked was maintained by the council's Parks Department. The Lumley's house had a chunk of ground right next door to it, and the beachfront where David Reid disappeared from was public property too. And so was the riverbank where he was found.

Something went click in Logan's head.

'Martin Strichen,' he said, pointing at the laptop's screen. 'He's on the sex offenders list. He always gets community service with the Parks Department.' He poked the map, smudging the blue circle he'd drawn over Seaton Park. 'That's how he knew those toilets weren't going to be used until spring!'

Watson shook her head. 'Sorry, sir, but Strichen was done for masturbating in a women's changing room, not fiddling with small boys.'

Insch agreed, but Logan wasn't going to be put off so easily. 'It's a swimming pool, right? So what do mothers take to the swimming pool? Children! The kids are too young to leave them on their own in the male changing rooms, so the mothers have them in with them! Little naked girls and-'