“I’m insulted you don’t think I know what I’m doing,” Allegra said. “I’ve dreamt about my revenge night after night. I’ve plotted it for weeks, months, years.”

“Revenge for what, exactly?” Jessica demanded. “What has anyone ever done to you?”

Allegra let out a brittle laugh. “Do you have any idea what it was like to be discarded by Emerald all those years ago? I was devastated. I felt so worthless and depressed I couldn’t get out of bed for months.”

She closed her eyes as she tucked her hair behind her ears, revealing huge diamond studs.

“Now all those stupid young girls will get to know what it feels like to be treated like a piece of trash. Why should I age alone when I can have company? Why should I be tortured by staring at gorgeous young faces on the cover of magazines? My magazines? It’s too much to bear.”

“You’re crazy,” Jessica said. “You can’t possibly think you’ll get away with this.”

“But I already have, darling.” Allegra cackled loudly. “Your father couldn’t stop me and neither can you. You both walked into a trap. Did you really think I’d want to employ the girl next door to represent my company? Once you arrived in Paris, it quickly became apparent you’d find a way to snoop around here. It made much more sense to invite you in and get rid of you as well. Two for the price of one. It was just a shame we had to ruin an Alexander McQueen gown in the process.”

Jessica bit her lip. Her instincts were right. Nathan had tried to keep her away from AKSC at first but then the plan changed and he sent her into a trap without any backup and the dodgy eyeshadow palette – a crucial gadget that he knew wouldn’t work.

“In a few weeks’ time, when those silly little girls realize there’s something wrong with the cream, it’ll be too late,” Allegra continued. “There’ll be nothing they can do to reverse the ageing process. They’ll be stuck with their ugly faces for the rest of their lives like Tyler and the others.”

“But you’ll be caught and thrown into prison,” Jessica said. “How is that revenge when you get to spend the rest of your life locked up? You’ll have thrown away everything you’ve ever worked for.”

“Wrong again. Starfish has arranged my new passport, safe passage out of the country and a new identity in exchange for a single vial of the Teenosity formula. It is, after all, unique and extremely valuable.”

She whipped a small metal canister out of her handbag and waved it at Jessica.

“For God’s sake, put it down,” Sam shouted. “If the lid comes off, you’ll release the nanoparticles and infect anyone within fifty metres who inhales them. Give it to me now and this could all be over.”

“I really don’t think so,” Allegra said. “It’s my ticket out of here and Starfish is expecting it.”

“It’s MI6 agent Nathan Hall, isn’t it?” Jessica said tersely. “He’s Starfish.”

“I don’t know his real name and I don’t care.” Allegra smirked as she carefully put the canister back in her handbag. “We weren’t on first-name terms.”

“How’s that even possible?” Jessica asked.

“Starfish is very private – just like me.” She hesitated and glanced over her shoulder. “To be honest, it’s been delightfully cloak and dagger. He used a voice disguiser on the phone as well as go-betweens whenever he needed to get a message to me directly. I’ve never done business like this before.”

Which made perfect sense when she was dealing with a spy – or rather, a double agent.

“How did you manage to find Starfish?”

“He found me,” Allegra replied. “Somehow, don’t ask me how, he knew I’d got Sam and cut me a deal that was too good to turn down. Your father got in the way and made a good fall guy until you interfered.”

“Why are you telling her this?” Lyndon appeared by Allegra’s side, grimacing.

She jumped a little. “What difference does it make now? We have to get rid of her and her father. Starfish said so. It’s part of the deal. We can’t go back on it now, darling.”

“Well, let’s get on with it instead of playing your stupid mind games as usual,” he said. “I’ve had enough of them. We’re wasting time.”

Jessica assessed the burly guards in front of her as the couple bickered. The men were taller and far more muscular than she was. She guessed they pumped iron. They were stronger but she still had the element of surprise on her side.

She lurched forward and brought her elbow up sharply. She struck the first guard under the chin with a resounding crack. He lost his balance and fell back a pace, startled. She advanced and performed a roundhouse kick, followed by one behind his knee. She wasn’t as strong or as steady on her feet as usual but she still managed to bring the man to the floor. The second guard lunged at her with a syringe but she knocked it out of his hand. She clasped her hands around his neck and pulled him down towards her. She brought her knee up as hard as she could, landing a blow in his solar plexus. He spluttered for breath but she kicked his feet out from under him.

“Jessica! Watch out!” Sam shouted.

She swung around but wasn’t quick enough. Lyndon struck her hard in the stomach, winding her. She fell to her knees, gasping for breath.

“It’s time we finally put this stupid girl and her dad out of their misery,” he said. “They’ve plagued us for long enough. Get her up.”

He clicked his fingers at the guards who’d managed to recover their breath. They pulled her roughly to her feet and dragged her down the corridor. Allegra swiped open a door, revealing a figure lying curled up in a ball on the floor. He looked like a corpse, with white skin stretched over gaunt, hollow cheekbones. It took her a couple of seconds to recognize her dad. He didn’t appear to be breathing. A slight tremor gave her a faint glimmer of hope.

“Dad!”

She struggled with the guards, who pinned her hands tightly behind her back. She longed to throw her arms around him but couldn’t break free. Her captors were too strong. Had he been injected with Teenosity as well? Was he going to age before her?

“What have you done to him?” she demanded.

“He’s sedated with the same drug as you were,” Allegra said lightly.

“Do you know what you’ve done?” she yelled. “You can’t give a drug like that to someone with M.S. He may never regain the feeling in his limbs like I did.”

“Do you think I care?” Allegra said.

Jessica tried to lunge at her but one of the guards twisted her arm harder. She cried out with pain.

“There, there, calm down,” Allegra said. “There’s no point getting all het up. It won’t help your father.”

“Wake up.” Lyndon shook him.

He heaved her dad to his feet. His eyes opened briefly. They looked glassy and rolled around in their sockets before closing again. His arms hung limply and his legs couldn’t hold his weight.

“Dad! It’s me, Jessica!” she shouted. “Wake up!”

His eyes didn’t reopen. He was locked in his own faraway world that she couldn’t reach. Lyndon heaved both her dad’s arms over his shoulders and dragged him out of the room. His head flopped back as if he no longer had any control over it.

“Please do something,” she said, turning to Allegra. “I’m begging you. You can’t do this. He needs to see a doctor. He’s ill.”

Allegra ignored her and followed Lyndon. Jessica’s mind whirred, trying to figure out what to do. She couldn’t make a break for it. Even if she did, she couldn’t possibly carry her dad single-handedly. She still felt weak and Sam was unsteady on his feet. He couldn’t help. They were at the mercy of Allegra and Lyndon. It was hopeless. They’d already tampered with her phones so she couldn’t call for help and there was no sign of the police. Becky couldn’t have checked her emails. She might not go online until tonight and by then it would be too late. They’d all be dead.

Lyndon led the group along the corridor. He hoisted her dad over his shoulders as they reached the stairs. Allegra’s stilettos clattered as she climbed up after him. They argued in hushed voices while the guards muttered into their walkie-talkies. As they reached the lab, three more guards joined them, armed with machine guns.

“This is where we have to part ways.” Allegra pushed Jessica into the clean room.

Lyndon dragged her dad in and backed away. She crouched down beside him. His breathing was shallow and laboured.

“Say your goodbyes to Mr Bishop,” Allegra said. “It’s the last time you’ll ever see him. He’s coming with us.”

He stumbled as a guard pushed him towards Allegra. He grabbed the work surface, trying to regain his balance.

Jessica rose to her feet. “What are you going to do to him?”

“We’re taking him to Starfish, along with the vial of his precious formula, in exchange for fifty million pounds.”

“No!” Jessica cried. “Starfish betrayed you. He’s going to hand him over to a terrorist. You can’t want that to happen.”

“Do you mean Vectra? He’s my number-one fan.” Allegra beamed at them. “Apparently he adores my pioneering work and my vision. He’s got great plans for you, Sam. He can’t wait to try out your creation on his enemies.”

Sam looked appalled. “I won’t be a part of this!” He tried to back away but a guard shoved him closer to Allegra, almost sending him sprawling to the floor again.

“That’s for you to argue with your new boss, not me,” Allegra said coldly. “I don’t care what you want. You’re useless to me now.”

“You can’t let Vectra get his hands on Teenosity!” Jessica exclaimed. “He could mass-produce the nanorobots and release them in shopping malls or football stadiums.”

“She’s right,” Sam said. “If Teenosity gets into an air-conditioning system, it could maim or kill thousands of people.”

“That’s none of my concern,” Allegra snapped.

Sam tried to launch himself at Allegra but he was too slow. Lyndon stepped in and poleaxed him with an elbow to the stomach. His head gave a sickening thud as it hit the ground. He lay motionless. Jessica tried to reach him but a guard shoved her back.

“You’d better not have killed him!” Allegra screeched.

“He’s unconscious,” Lyndon said, checking Sam’s pulse. “Now for God’s sake, let’s get on with this. We should have blown the labs by now. We’re late for the rendezvous point. Starfish will come here looking for us before long.”

“Starfish can wait,” Allegra said, glowering at him. “I want to enjoy this.”

Lyndon glared back. “Well, if you won’t give the order, I will.”

He clicked his fingers and two guards peeled away to the furthest corner of the lab. They crouched down, their backs turned.

“What are they doing?” Jessica said.

“They’re setting timers for the explosives,” Allegra replied. “There’ll be nothing left of the building when I’m finished with it. I can’t risk any evidence being discovered when I’ve left, including your disfigured bodies. You see, I’ve planned something special with Starfish and Vectra, just for the two of you.”

She pointed at the ceiling of the clean room.

“Look up at the vents above your head, Jessica. Soon, a lethal, aerosolized dose of Teenosity will be blasted out. Within seconds, your body will start decaying from within. You’ll age from fourteen to eighty in sixty agonizing seconds. Dying in the blast will be a relief after this.”

Jessica stared at her, horrified. She was mad enough to carry out her threats.

“That’s right. It’s not going to be pretty,” Allegra said. “I imagine it’ll be extremely painful but Starfish and Vectra both agreed it would be a useful experiment. Sam was right. Contaminating air-conditioning units must be a natural next step from this. Let’s see how Teenosity works airborne, shall we?”

“No! Don’t!” a voice said weakly.

“Dad!” She threw her arms around his neck as he struggled to sit up.

“So you’re with us after all, Jack,” Allegra said.

“Please,” he whispered. “Spare my daughter. She doesn’t deserve this. Kill me, but let my daughter live.”

“No, Dad! I won’t leave you.”

“How touching,” Allegra said. “I’d hate to be the one to separate the two of you. You can die together. But first…”

She stepped forward and ripped the emerald ring from Jessica’s finger.

“I won’t make the same mistake again. Starfish said to look out for this.” She examined the ring. Her fingers expertly flicked open the secret catch. A laser shot out and died again as she snapped it shut. She placed the ring on the counter.

“Amazing what MI6 can do nowadays,” she said, “but I’m feeling particularly generous today, so you can have this back, as it’s worthless.”

She threw an object at her.

“Starfish said it belonged to your mother and you’d want to wear it when you died.”

Jessica reached out and caught her mum’s necklace. She held it tightly in her fist. She wished she’d grabbed the flamethrower or compact off Nathan and used them on him when she had a chance. Only he could have known how important the pendant was to her. Her mum wore it in the photo he kept in his wallet. He kept trophies too, just like Allegra.

“It’s tragic when one loses their mother so young,” Allegra said suddenly. “We have more in common than you think.”

“I really don’t think so,” Jessica spat back. “You’re certifiable. I’m not.”

Allegra shook her head. “I lost my mother when I was four, just like you, and things were never the same again. My stepmother never understood me. She never wanted me to model. She never wanted me.”

Her eyes misted up as the guards rejoined her. She ignored Lyndon, who impatiently checked his watch.

“Think of your mother now,” Jessica said urgently. “She wouldn’t want you to do any of this.”

“I tried to tell the voices but they wouldn’t listen.” Allegra started to sob. “They’re too strong.”

“What voices?”

“The voices in my head.”

Jessica walked towards her. Allegra had lost her mind, but Jessica had found a chink in her madness. If she could get her to talk more about her mum, she might have a chance of getting through to her.

“The voices are talking to me again,” Allegra said, a hint of a smile hovering on her glossy, scarlet lips.

“What do they say? Are they telling you to let us go?”

“No. They’re saying they’ve had enough of your delaying tactics.”

Allegra hit a button on the wall and the door slid shut, sealing them into the room.