He took one last sweep of the park and lowered the scope, placing it back into the rucksack, and retrieved a small sandwich bag at the same time. He placed the sandwich bag in the crook of a small tree and headed back to the wall of the park, comfortable in the security of the dark. He needed his sleep and to re-check his plans for the next murder. He'd leave the rest of the night to the guards.

McEvoy stood at the edge of a large car park used during the day by numerous coach companies to offload tourists. A metal bar blocked access, a sign attached to it stating that it was padlocked at nine o'clock each evening. At the far corner, a short distance beyond the car park, the tall cross rose tall into the sky, silhouetted against the dull, orange-tinged clouds. Over a million people had gathered at its base in 1979 to hear Pope John Paul II say Mass. Now it cast its shadow over a murder scene. He could hear another car approaching those parked along the roadside and turned to examine the new arrival.

Elaine Jones' diminutive figure stepped out onto the pavement, her eyes drinking in the scene, trying to get her bearings.

McEvoy started to head towards her and called out her name. 'Elaine!'

She glanced left, noticed him approaching and waited.

'No Billy?' he asked as he neared.

'Decided not to disturb him.' Even at this hour she sounded chirpy. 'Lad needs all the beauty sleep he can get.'

'Yeah, sorry it's so late,' McEvoy apologised. 'We found the body at around midnight.'

'Well, it can't be helped, can it? You find them when you find them. It's better to look at her now than in the morning. Ah, ah,' she admonished him as he pulled to a halt. 'The cheek kissing business. Come on.' She patted a cheek with her index finger. 'I'll get you trained yet.'

McEvoy rolled his eyes, leant forward and kissed her on both cheeks.

'Doesn't hurt, does it,' she teased. 'And it puts me in a good mood. So where am I heading?' she asked, moving to the back of the car to retrieve a bag.

'The body's in under the trees covered by a sheet.' He gestured with an arm. 'A runner doing a couple of circuits. I think she was probably attacked out at the path and then dragged into the darkness. There's a trail evident through the grass. One of the paramedics has confirmed she's dead and took some temperature readings. He's over in the ambulance there.' He pointed along the road and they started to walk toward the crime scene.

'I'll talk to him afterwards. Just make sure he doesn't disappear on me, will you,' she instructed. 'So any ideas as to how she died?'

'Well, her face has been smashed in and her toes cut off. I'm not sure if they killed her though. It was dark and I didn't want to mess things up too much. I just made sure she was dead.'

'Her toes cut off?' Elaine repeated.

'He left one pinned to a nearby tree with a note.'

'First the sword, then the paint, now toes. Well, he's certainly creative.'

'He's a sick, depraved bastard, is what he is,' McEvoy stated, a quiet anger in his voice.

'That as well,' Elaine agreed, keeping her tone light-hearted. 'Do you have any lights so I can see what I'm doing?'

'We're waiting on the crime scene people to arrive with some arc lights. I'll find two volunteers. They can go across with you and hold a couple of torches each. How's that sound?' McEvoy hazarded.

'Well, I guess it'll have to do for now,' she conceded, clearly not happy with the arrangement, liking things to be performed professionally.

A dark Audi pulled up on the far side of the road. A woman with long, dark brown hair eased out of the driver's seat and smoothed down the jacket of her well-tailored, mid-grey business suit. Beneath the trousers she wore flat black shoes. Under the jacket was a white blouse with stiff collars, open a couple of buttons to reveal a small, gold cross on a chain. She surveyed the scene, picked out McEvoy and headed over to him.

'None of my lot here yet?' she asked as a greeting.

'Not that I'm aware of, Jenny,' McEvoy replied. 'You ready for this?' he asked, aware that this was Jenny Flanagan's first case as a detective inspector. The transfer to NBCI had only taken place a few days earlier, though she had previously worked for the unit as a detective sergeant. 'Our killer's a very sick bastard.'

'Don't worry, I'm ready. I've been waiting my whole career for this; to lead a murder investigation.'

'Well, they're obviously paying you good money,' McEvoy said, nodding at the car.

'It's not mine, it's Brian's. I've left him with my Peugeot, not that he knows it yet. I'm still hoping he might swap on a permanent basis.'

'Fat chance. Look,' he said, the pleasantries over with, 'what I want you to do is take charge of the crime scene. Make sure it's all taped off properly and that people know what they're doing. Someone will need to go and talk to the victim's husband. You if needs be. We need to find out everything we can about her what she was like, where she worked, who her friends were, everywhere she'd been in the last two weeks, whether she knew Laura Schmidt or David Hennessey the two other victims. Anything you can think of. Something links these murders together. We need to know what it is.'

'You want me to interview her husband?' Flanagan asked, aware that if she was doing that then she wouldn't be able to co-ordinate things at the murder site.

'I don't care who does it, as long as it's done,' McEvoy said, knowing that he didn't want to do it. They were too emotionally charged; too depressing.

Flanagan nodded in acknowledgement. That would land on one of the DS's lap.

'We're still waiting for the local superintendent to turn up,' McEvoy continued, 'and also the crime scene people. Can you try and find out where the hell they are? We need to get some arc lights from somewhere and we also need the site processed. He's left us another note and I want to know what the hell it says.'

'I'll get on it right away,' she replied, pulling an ultra thin phone from her pocket and starting to move away.

Two more cars turned up in quick succession. Two of Flanagan's DSs Diarmaid Savage, wiry and athletic with a shock of black hair just past the stage of needing a haircut, and Declan Greer, stocky, with a gut just starting to hang over his waistline.

McEvoy sat, head tipped back, in the front passenger seat of a garda car, the seat pushed as far back as possible to give his long legs room and reclined a little from its normal position. There was a light tap at the window. He rolled his neck slightly, but didn't open his eyes. The tap was repeated. He tipped his head to the left and opened his right eye. Michael Foster, the crime scene manager, gestured through the window. McEvoy wondered how long he'd been asleep. Whatever it was, it wasn't enough.

He pulled himself forward, pushed open the door and looked up at Foster. It was raining now, a steady drizzle.

Foster was wearing a luminous yellow jacket, his collar turned up, his short, grey hair wet with the rain. 'We've processed the note,' he said. 'It's a quote plus what looks like a grid reference.' He held out a clear plastic evidence bag.

McEvoy reached out and took the bag. He read through the plastic.

The Rules

Chapter Three I: Planning K.

"Serial killers who kill for years plan their every move. They are rarely impulsive and despite their internal conflicts, unstable emotions, and rage at the world, they can present themselves as an ordinary member of society. They construct 'murder kits' containing essential items such as their weapon of choice, duct tape, gloves, and a change of clothes. They select their site of attack and plan their routes to and from the scene. They enjoy the planning and they revel in the duplicity of killing an innocent victim and getting away with it."

53,21,41.72, 06,19,31.88.

'Jesus!' McEvoy whispered sharply. He read it again. 'He's telling us that he thinks he knows himself; knows exactly what he's doing. That he's enjoying this whole sick episode the planning, the killing, the chase. Everything. The guy's a complete psycho.'

McEvoy paused and read the note a third time. 'We need to know where he's getting these quotes from.' He slapped the bag. 'You got anything else?' he asked, easing himself up and out of the car. He pulled up the collar on his suit jacket, realising his coat was in his car back at the start of Grainne Malone's circuit. Off to his right he could see the murder site covered by a canvas gazebo trying to keep the rain off, though it was soaked in dew in any case. The whole area was lit by bright arc lights.

'Seems it was the little toe of the left foot in the bag,' Foster said. 'We've got a few other bits and pieces blood and hair samples. Maybe the victim's, maybe not. A few good footprints.'

'How about the numbers? Do we know where they refer to?'

'We're working on it. We think it's latitude and longitude, rather than a grid reference. He's pointing us to another site.'

The business card had been found pinned to a lime tree near to aras an Uachtarain, the President's palace. A clear, plastic sandwich bag was pinned to the tree, a severed toe nestled in a corner, the folds of a note resting on top.

McEvoy read the note through an evidence bag.

3a. Plan meticulously from start to finish.

53,21,27.63, 06,19,23.92.

He pursed his lips and scratched at his scalp, thinking through its significance. 'He's trying to lead us on a merry dance, trying to waste our time by chasing after your one's toes and his damn notes; giving himself more time to get on with planning and executing his next murder.' He paused, staring off across the park, before focusing his gaze back on the note. 'Well, I guess we haven't got a choice, have we?' he muttered, shaking his head in disgust. 'For feck's sake!'

Jenny Flanagan headed towards McEvoy as he approached the murder scene. As they neared each other she started to talk. 'We've found another toe and note. Over there by the outer wall of the ambassador's house, pinned to a tree right at the end of the walkway leading up to the papal cross.'

'Another's been found up by aras an Uachtarain,' McEvoy answered. 'He's left us a trail to follow. Parcelling his feckin' chapter out in bite-size chunks.'

'Well, he certainly has balls, killing someone within a hundred metres or so of two of the most prestigious addresses in Ireland. Addresses with some of the best security arrangements.'

'You sound like you admire him,' McEvoy snapped. 'He's a cowardly bastard who kills innocent victims.'

'I ... I wasn't,' Flanagan stammered, a red blush rising from her collar. 'I didn't mean ...'

'Forget it,' McEvoy said, annoyed at himself for lashing out at a colleague. 'What did the note say?'

'It says it's a master rule. Something about analysing all mistakes, not repeating them or trying to correct them. It's over with Michael Foster.'

They walked to where the forensic officer stood, talking to a uniformed guard.

'You've found a note?' McEvoy asked, halting their conversation.

'I didn't,' Foster answered. 'One of the local guards did,' he gestured his hand at his companion.

McEvoy nodded in thanks and continued. 'What does it say?'

'It's in the van.' Foster walked the few metres to a white Ford transit, opened the rear door and passed the note to McEvoy.

McEvoy read through the clear plastic bag.

Master rule: If you make a mistake, however small, do a full analysis and do not do it again. Do not try and correct it. Any attempt at correction is likely to lead to more problems than it solves.

He stared at the sheet in silence, his mind a complete blank, reading the words but unable to give them meaning. Eventually he lifted his head and said to Foster, 'You'd better let the others know you've found this in case they're hunting for it later.' He handed the note back. 'I'm going to get a coffee,' he said to no one in particular. He could do with a rest not caffeine; there was no question of sleep, however, the clock was already counting down to the next murder. He glanced at his watch ten minutes past six wondering whether it was too early to ring his daughter. He'd better leave it at least another hour.

'We've just found the fifth toe and note,' Diarmaid Savage said, 'but there was no business card. I thought I should let you know. We've had a good scout around, but there's no sign of it.'

'Four makes sense,' McEvoy said. 'There's four more murders to go. He's counting down. I doubt you're going to find any more. What do the notes say?'

Savage read them out.

3b. Scope out the victim as little as possible - enough to feel confident that things will work out as planned, but not enough that you get noticed.

53,21,02.47, 06,18,57.60.

3c. Do a full reconnaissance of place and escape routes. Make sure all options are tried and tested.

53,21,05.07, 06,20,03.72.

3d. Have contingency plans for all stages of the murder.

53,20,51.21, 06,20,03.87.

3e. Do not confide in anybody. Ever. You might be able to trust your own mouth, but you can never trust anybody else's. 53,21,03.04, 06,20,34.74.

'That's it. We're going to head on to the next point. He seems to be leading us round the park. The third point was way off towards the Wellington Memorial, up on top of a small hill opposite the fort. We're now down near the Chapelizod exit.'

'Right, okay. Keep going,' McEvoy instructed. 'I'll talk to you later.'

McEvoy ended the call. He leant back against the car's bodywork and felt the clammy, cold sweat on his brow with his palm. There was a dull ache behind his eyes, the start of a headache forming higher up in his forehead. His suit was damp from the light drizzle, his shirt sticking to his back. They were going too slow. He was going to kill again soon. And what were they doing? Wasting time trying to locate toes hidden around the Phoenix Park! He needed to be doing something, but had no idea what.

He moved his hand down and rubbed his eyes through their lids. All he wanted was the murders to stop and a couple of days' sleep. That and a cigarette. Maybe he was going to have to try the patches. He pushed himself forward and moved off, hunting for someone to talk to or something to do.

'Hello?'

'Caroline, it's Colm.'

'Where the hell have you been?' she snapped. 'You could have called. We've been worried sick. So's Mammy. You didn't call her.'

'Yeah, sorry,' McEvoy conceded. 'I decided I'd drop in on the way home, but I got another phone call. I've been in the Phoenix Park all night. This time it was a jogger.'

'God almighty,' Caroline whispered, her anger re-directed away from McEvoy. 'Are you any nearer to catching the bastard? He should be strung up in front of their families,' she said with vigour. 'Strung up,' she repeated.

'We're still working on it,' McEvoy answered neutrally. 'He's not leaving us much to go on and he's moving too quickly. It's difficult to keep up.'

'And have you managed to get any sleep?' Caroline asked, mothering him, knowing that he wouldn't be looking after himself.

'A quick doze here and there. Look, I haven't got long, is Gemma there?'

'Yeah, I'll get her. Take care of yourself, okay? You're no use to anyone ill.'

'I know, I know,' McEvoy conceded, stifling a yawn.

There was a brief pause.

'Has there been another murder?' Gemma asked, already knowing why her father hadn't contacted her.

'At about nine last night. I'm still at the scene. Look, are you okay?'

'I'm grand.' She said it as if there was no reason why she shouldn't be, that it was perfectly natural for her father to be out until the early hours investigating a serial killer. 'I'm just getting ready for school. How about you? Have you been drinking and eating enough?'

'Of course,' McEvoy lied. 'I'm going to need you to stay with Aunt Caroline again tonight. I'll try and drop in so we can catch up.'

'If you can, you can, and if you can't, that's fine,' Gemma sang.