‘Have you got any of your formula here?’ he asked. ‘I’d be keen to see it.’

‘No, I haven’t,’ she said firmly. ‘I ran out, need to make some more up.’

He watched her eyes for signs of a lie. Hard to tell. He paused for a moment. ‘So, do you think there’s any chance you might let me have a copy of your research notes?’ he asked, hoping the request didn’t come over as too bold. He toyed with the idea of offering her money for them, but that would have made her instantly suspicious of him.

She wagged her finger. ‘Ha ha. No way, pal. Anyway, you think I’d be dumb enough to write down the formula?’ She tapped her head. ‘It’s all in here. This is my baby, and nobody’s getting their hands on it.’

He grinned ruefully. ‘OK, forget I mentioned it.’

There were a few seconds of silence between them. Roberta looked at him expectantly, then placed her hands flat on her knees as though to signal the end of the interview. ‘Anything else I can help you with, Ben?’

‘I won’t take up any more of your time,’ he said, worrying that he’d blown it by asking to see her notes. ‘But if you get any major breakthroughs, will you give me a call?’ He handed her a card.

She took it, and smiled. ‘If you want, but don’t get too excited. It’s a slow process. Call me again in, say, three years’ time.’

‘It’s a date,’ he said.

Roberta Ryder suddenly looked much less the austere scientist, with her wavy dark red hair let down past her shoulders and the labcoat switched for a denim jacket. ‘Michel, I’m going out. You can take the rest of the day off, OK?’ She got her sports holdall from the bedroom, grabbed her car keys and headed off for her weekly session at the martial arts centre across town in Montparnasse.

As she drove she was thinking about her interview with the journalist Ben Hope. She always had to come over like the ballsy, tough, defiant maverick scientist who was going to show ‘em all one day…it was the image she clung to. Nobody knew about the fragile reality of her situation. They didn’t know about the fears she had, the worries that kept her awake at night. The day she’d been fired from the university, she could so easily have packed a bag and jumped on the next flight home to the States. But she hadn’t. She’d stayed to tough it out. Now she was wondering at the wisdom of that decision. Had all the sacrifices she’d made been worth it? Was she just chasing rainbows, kidding herself that the stand she’d taken was ever going to make a difference? Soon her money would be all gone, and she’d have to try to find some supplementary income from somewhere-maybe private science tuition for schoolkids. Even that might not even bring in enough to scrape by on, pay Michel’s meagre wages and fund her research. The next two or three months would tell whether she could go on, or whether she’d have to give it all up.

She got back to her apartment at around 5.30. Her legs felt heavy as she climbed the spiralling, echoing stairs to the third floor. It had been a tiring session that day, and she was hot from the rush-hour traffic.

When she reached her landing and took out her keys, she found the door unlocked. Had Michel come back for something? He was the only other person with a key, apart from the concierge. But it wasn’t like him to leave the door open.

She went inside, peering into the lab room through the slightly-open door. ‘Michel? You there?’ There was no reply, no sign of him. She went into the lab.

‘Oh, Jesus’

It had been turned over. Files spilled all over the floor, drawers up-ended, everything gone through. But that wasn’t what she was standing gaping at. It was the big man in the black hood who was rushing towards her.

A gloved hand shot out towards her throat. Without thinking about it, she blocked the move by throwing her hands up and outwards to deflect his arms aside. The surprised attacker hesitated for half a second, long enough for her to follow up her move with a low stamping kick to his knee. If it had landed it would have ended the fight there and then. But he skipped backwards just in time and her foot only grazed his shin. He moved back with a grunt of pain, stumbled and fell heavily.

She turned and ran. But he threw out a big arm and tripped her, sending her sprawling to the ground. Her head whacked the wall and she saw stars. By the time she was on her feet he was just two metres away with a knife in his hand. He came at her, lifting the knife high to stab down at her.

This was something Roberta knew a little about. A trained knife fighter keeps the weapon close to his body and stabs outwards, using the rotation of his back muscles to deliver lethal force to the blow. Very little can be done to block the move or take the knife off them. But the downwards stab, holding the knife in an underhand grip, was a different matter. Theoretically, she knew she could block this. Theoretically. At the karate club they’d only ever practised this move with a soft rubber blade, and then never at full speed.

The very real blade flashed down hard and fast. Roberta was faster. She caught his wrist and levered it down sideways while with her other hand she wrenched his elbow the other way with all her strength. At the same time she launched herself into him with a hard knee to the groin.

The move worked. She felt a terrible cracking as his arm broke. Heard his scream in her ear. His face contorted in agony behind the mask. The knife fell, and his twisting body fell on top of it. He hit the floor, landed writhing on his belly, and screamed again.

She stood poised over him, staring in horror, as he contorted and rolled onto his back. The knife was buried deep in his solar plexus. He’d landed on it, driven the blade in with his own weight and momentum. He clawed desperately at the handle, trying to pull it out. After a few seconds his movements slowed, the convulsions slackened, and then he lay still. Blood spread slowly outwards in a slick stream across the tiles.

She screwed her eyes shut, knees quaking violently. Maybe when she opened them, there wouldn’t be a dead guy lying there in a pool of blood. But no, there he was all right, staring up at her glassily, mouth half open like a fish on a slab.

Every nerve in her body was screaming at her to run, but she fought the impulse away. Slowly, her heart in her mouth, she crouched down next to the body. She reached out a trembling hand and slipped it into the front of the dead man’s black jacket. Inside she found a small diary, half-soaked in blood. She turned the dripping pages, shuddering in revulsion at the blood on her fingers and looking for a name, a number, a clue.

The diary was almost completely blank. Then on the last page she found two addresses, scribbled in pencil. One was hers. The other was Michel’s.

Had they got to him? She dug out her phone, feverishly scrolled down her address book entries as far as ‘M.Z’, and hit the dial button. ‘Come on, come on,’ she muttered, waiting.

No reply, just his answering machine.

She wondered whether she should call the police. No time for that now, she decided-it would take an age to get through the receptionists and she had to get over to his place right away. She stepped over the corpse and opened the front door a crack.

All clear. She locked the door behind her and bounded down the stairs.

The car screeched to a halt at a crazy angle outside Michel’s apartment building, and she ran to the doorway. She buzzed the button next to his name on the intercom panel several times, kicking her heels, tension mounting.

After two or three minutes a laughing couple came out of the building and she slipped inside. She found herself in a dark, stone corridor leading to the stairway, past the concierge’s door and into the central courtyard. Michel’s apartment was on the ground floor. She thumped on his door. No response. She ran back through the foyer and into the courtyard. Michel’s bathroom window was slightly open. She scrambled up to the window ledge. It was a tight squeeze, but she was slim enough to wriggle through.