She slid into the car and tried to ignore the pounding of her heart. They pulled away from the curb and headed down the road towards Kings Cross station. Neither of them spoke.

Being in such sudden close proximity to the man – a stranger – was a peculiar feeling. She hoped her nerves weren't as obvious as she thought they must be; she was so tense, she could barely sit still.

There was a vaguely sweet smell that she couldn't put her finger on - air freshener, probably. The interior was unremarkable. She glanced behind her; the back seemed clean, but there was a child's car seat. She saw a few toys strewn around: expensive-looking wooden animals, painted bright colours. Harry felt queasy and relieved in equal measure. Queasy at the thought that someone could pick up a prostitute in the same vehicle he transported his young children in; relieved that surely their presence made him less likely to be the killer. The man they were hunting was a loner - there was nothing in the profile to say that he was a family man.

When they reached the traffic lights, he spoke. "Mind if I drive a bit further?" His voice was soft and faintly cultured. "There's a place under the St Pancras railway arches I know where we can have some peace and quiet, but we have to go around the one-way system to get there."

A memory flashed through her mind: she and Dempsey driving around the one-way system three days ago, arguing. Dempsey. She wished he were here with her.

"Yeah okay," she said, hoping her cockney accent would stand up, "but I have to be back for another punter soon. Time is money an' all that."

"Don't worry, I'll pay you for any time we go over."

He looked over, appraising her. She felt his eyes on her legs in their fishnet stockings. Her tiny skirt had ridden up almost to her crotch and Harry, unaccustomed to any indecorum, felt terribly exposed.

She sensed, rather than saw, him smile. "You're new," he said. "I haven't picked you up before."

"Yeah, that's right. I usually work in Shoreditch. Just keepin' a mate company tonight."

"Well I'm glad you did." They were moving around the junction at the centre of Kings Cross, and the lights from the bars and clubs afforded her a better look at him. Just like the other punter, he was non-descript. Forties. Pale, thinning hair. Harry thought of Tina describing the man whose car Liz had got into. "Not skinny. Not old, not young." It covered half the population. Still, she shivered.

"Cold?" He reached forward and adjusted the heater on the dashboard.

"A bit."

They drove in silence for a while. They were almost in Islington before the road looped back towards St Pancras. The frozen streets were quiet, with only the odd drunken reveler in evidence.

What do I tell him when we stop and he expects me to perform?

She decided just to come clean about the police operation. It would be embarrassing for him, and given his situation, he was bound to be terrified of being arrested and exposed but she could reassure him that no charges would be pressed.

They had reached a quiet side street.

"Hey," he said suddenly. "Did you know Liz?"

"Liz?"

"The girl that was murdered. Her spot was right where I picked you up."

Involuntarily, her heart started hammering again.

"Oh yeah," she willed herself to be calm; "I mean, I didn't know her really. That's why I'm here though - lookin' out for my mate. She feels vulnerable bein' alone. You know?"

"I can imagine."

The car had slowed to a crawl. To their right were the railway arches and built underneath each of them, what appeared to be lock-up facilities. The street lighting was minimal.

She was getting more uncomfortable by the minute. The darkness meant that her other senses were heightened, and she didn't like the feeling she was getting from the man. The sweet smell was in her nostrils: cloying, unpleasant. It was time to end it. She waited until he stopped the car under an archway.

'Sir" she said, in her normal voice. "I'm afraid this is a little awkward under the circumstances. You see I'm actually a police officer investigating the prostitute murders that have been occurring in this area."

He didn't react at all, just looked at her.

"I know who you are. I realized when you got in beside me," he said. Then he smiled. She was confused.

"I'm sorry. Do I know you?"

Their eyes met.

"I'd been expecting you," he gazed at her steadily. "Ever since I saw you and your colleague nosing around the other day. Fancy picking you up, though - I honestly didn't recognize you." He glanced down her body.

"What a wonderful transformation."

Harry's stomach had turned to liquid. She tried to speak, but her throat seemed to have closed up.

Suddenly, he reached down and retrieved something from below his seat. It was a red rose.

"You make a truly authentic whore, do you know that?" His voice was flat, emotionless.

The smell made sense. Terror like she had never known was coursing through her veins. Oh God, oh Holy Christ, it's him. It's the Suitor.

Then instinct took over. In one movement, her gun was out from the concealed holster and she was yelling, at him and down the wire to the surveillance unit, simultaneously.

"Get your hands up! Get them up!" Chas, Tom – I need back up NOW. Location is St Pancras railway arches off Euston Rd. Just get here, do you read me?"

But instead of putting his hands up, he started the engine. He reversed the car, and sped off again. Harry shouted desperately. "I said stop! Stop, or I'll shoot!"

He ignored her completely. They were traveling away from the railway, in the direction of Camden Town.

In the distance, she could hear the whine of a police siren. She still had the gun trained on him, but the situation felt as if it was slipping out of her control. They came to an industrial estate, and abruptly, he turned into it.

"You've got ten seconds to stop this car, or I'm going to shoot you," she ordered him. Suddenly, he slammed on the brakes, throwing her forward onto the dashboard.

Before she had chance to recover, he lunged at her and grabbed the gun. His homely, middle-aged appearance belied his strength, and her wrist was snapped back painfully, forcing her to let it go. Then the weight of his whole body was over her. She struggled beneath him, but he grabbed her hair and began to slam her head against the passenger window.

Just before she lost consciousness, she reached down and pushed the door handle. She fell backwards onto the pavement as the sound of the siren became deafening. The man pulled the door shut and floored the accelerator.

The squad car came squealing around the corner. Harry was lying crumpled on the pavement; the maroon car was nowhere in sight. Dempsey took seconds to reach her. She was unconscious, and blood was running from a wound on her temple. He touched her neck and felt the weak pulse there.

"Get an ambulance Chas, quickly!" he cradled her head.

"You're gonna be okay baby," he whispered.