"It's Gem." I stabbed the video-call button for the tenth time as I paced our office. "It has to be Gem."

"Yes," Alex said calmly. He was perched on the edge of his desk, his own tabphone in hand. "It's Gem. But Dixon's dispatched PRBs to her flat. She'll be fine."

"Then why isn't she picking up?" My voice rose, and I took a deep breath, trying to level it out again. I had to remind myself that I was a detective inspector and not a shrieking parrot. "Have you tracked where the message came from?"

"A tablet in Socrico Library."

My call to Gem rang out.

"Oh, for fuck's sake, pick up!" I slammed my fist into the glass desk, and there was a satisfying crack.

Alex flinched. "Amber -- "

My tabphone buzzed. I extracted my bleeding knuckles from the glass cobweb and answered the incoming call. "Gem! Finally."

She beamed on my screen, hot pink hair let loose from its pigtails and arranged so that it hid most of the bruising around her neck. "Hi, Amber. I only just got in. The policeman said he could take my statement at the scene, but then I had to persuade my boss to let me come home early. He was surprised when I asked -- the cheek! And -- "

"Gem, listen very carefully," I said. "Your life is in danger."

Her smile fell. "What?"

"Your robot saved you this morning, but Maxx Ackerman isn't giving up. He killed Zoe, he killed Bryony, and now he's coming after you. PRBs are on their way to your flat right now, and I'll come to guard you personally as soon as I'm done here."

"I'll come, too," Alex said softly.

"He shouldn't try anything until tonight," I continued, "but don't leave home, just in case. You can't let yourself be caught alone."

"But my boss wants me to go back to The Silver Star later -- "

"Call in sick. Do not leave your flat. If you leave your flat, you'll leave our protection. Am I clear?"

She gulped. "Yes, ma'am."

"Good. Now, sit tight and try not to worry. You'll be safe inside."

***

By the time the lights had turned off and we'd finished work, we still hadn't located Maxx. Alex and I walked to Gem's flat, situated near The Silver Star, in silence. A handful of PRBs were standing outside the building, and we found two more when we reached the entrance to her home.

I rang the doorbell, and the camera gave me automatic access. But Gem must have been standing right on the other side, because she opened it herself. "Amber!"

"Hello." I tried to smile and failed miserably. "You can relax now. You officially have six robots and two humans guarding you."

Her shoulders sagged. "I'm honoured. Come in."

She stepped aside, and we squeezed past her into the narrow hallway. Another PRB was lingering there.

Once Gem had shut the door, I said, "Don't answer it yourself again."

"Okay." She looked between us uncertainly. "But...why is this happening?"

I exchanged a tired glance with Alex.

Five minutes later, we were nestled in Gem's living room with three mugs of tea. Mine, shaped like a hippo, was resting on the wobbly coffee table. Hundreds of fairy lights were strung back and forth across the midnight ceiling. The walls were pink, the carpet was jade green, and the sofas were covered with ruby red blankets. Bubble-gum scented tea lights burned on the windowsill. Lace curtains were drawn across the glass, hanging perilously close to the flames.

Alex sat next to me. Gem was on the other side of the coffee table, hugging a mug that looked like a panda. She was biting her lip, but she had more colour back in her cheeks now that she was drinking sugar. I'd watched her put five teaspoons in.

"Right," I said. "Here's the short version. On Monday night, Maxx killed Zoe on Terra Road. He wanted her out of the way so that he could woo you. They'd just argued about an affair -- which had proved how much her presence limited his desires. Then in the early hours of Thursday morning, Maxx killed Bryony on Kings Road. He'd been having the affair with her, but on Wednesday night, he'd tried to break it off. She'd refused to leave him. He got rid of her.

"This morning, Maxx propositioned you again. When you rejected him, he tried to strangle you. Then he posted a message to the Socrico Police Xplora page warning us of a final murder."

All the colour had left Gem's cheeks again. "B-but if he likes me, why...?"

"Lots of murderers claim to love their victims," I said. "The problem is that their love is obsessive -- and possessive. When you rejected Maxx, he decided that if he couldn't have you, no one else could. So he tried to kill you." My hands tightened around the hippo.

"I thought he just lost his temper," Gem said. "He didn't look like he was really thinking. I mean, that seems a bit logical, even if the logic is twisted."

Alex put his mug down. "He was thinking logically enough to taunt us this afternoon."

The doorbell buzzed. "Gem, Cassia is here. May she come in?"

I stared at Gem.

"Oh, I invited her," she explained. "Yes, come -- "

"No, let me do it." I stood up. "Just in case Maxx is nearby."

I drew my pistol and went into the hallway, careful to plant each foot on the floorboards quietly. When I was behind the door, I raised my weapon. "Come in."

The door swung open.

My older sister was standing on the other side, wearing a blue skater dress and open duffel coat. She cocked an eyebrow at my gun and raised her hands in surrender. "Hello to you, too. If you're that concerned about Gem, you should have told me she's in danger."

I scoured the corridor behind her, then slowly lowered my weapon. "Who did tell you?"

"Gem. She sent me a frantic message about murderers and police guards. I picked it up after work. What the hell is going on?"

I sighed. "Come in, and I guess we'll explain everything again."

***

Cassia sat next to Gem like a fairy tale princess in her blue dress while Alex and I talked about the investigation. Once we'd finished, she remained still for a long moment, processing. Then she stood up, pulling her platinum hair over one shoulder. "I think this calls for more tea."

She tossed me a stern look, which I unfortunately knew well. We need to fucking talk.

I followed her into the kitchen. It was short and square, with a peeling blue pine table in the centre. Gem's worktops were littered with an assortment of liquorice, wet apples, a whisk, and a light bulb. What she'd been up to when she'd left it like this, I had no idea.

"Why didn't you tell me?" Cassia went straight to the cupboard containing mugs and withdraw one shaped like a fox, slamming the door.

"Because a few hours ago, I was back at the station only just realising it for myself!" I said. "My priority was to try finding Maxx, then to get over here when that failed. Then I had to explain what the fuck is actually going on to Gem, and then you showed up!"

Cassia looked down at my hands, and I realised that I'd balled them into fists. She turned away and put the kettle on. "All right. Sorry."

We listened to the kettle boil. She chucked a tea bag in her mug before pouring the water in.

"What are you dressed up for, anyway?" I softened my voice. "Wanted to see the murderer in your finest?"

"I was going out for dinner with Miles. Then he cancelled on me to work late, and I finally read Gem's message and came here."

I frowned. "You told me a few months ago that Miles hasn't taken you out for ages. He shouldn't have ditched you."

"I would have cancelled on him anyway to be with Gem."

"That's not the point."

"Ambie, he couldn't help it." She looked at me sharply. "You don't usually give him a hard time."

"No...but I feel like you're worried about something -- "

"Amber," Alex said.

I turned around. He was standing in the doorway, his face grave. Gem was crossing the kitchen towards me. She held up her tabphone with wide eyes.

There was a message from Maxx Ackerman.

I'm coming for you.

***

"It was sent from Socrico Library again," Alex said five minutes later. We were back in the living room, waiting for him to trace the messages.

I frowned. "We told the staff to let us know if they saw him."

"They must have missed him."

We lapsed into frustrated silence. PRBs clanked up and down the hallway outside. Gem bit her thumbnail, pale again.

I drew my pistol and put it on the coffee table. Sensing my hint, Alex did the same.

"Okay, we're ready." I gestured at the weapons before us. "So...why don't we think about something else while we're waiting?"

Another awkward silence filled the air.

"Maybe I could put the TV on quietly?" Gem suggested.

"Sure," I said.

She used her tabphone like a remote control and brought the glass screen on the wall to life. None of us really looked at it. Cassia coaxed her into a conversation about her pretty mug set. I just waited, keeping an eye on the time. Alex did the same.

An hour crawled by. Gem tucked her legs up and dragged a red blanket across herself and Cassia. They were talking about a mutual acquaintance now, but my sister was not as relaxed as she'd encouraged Gem to be. She was gripping her tabphone tightly enough that her knuckles had turned white.

Gem suddenly looked at us. "Hey, we haven't talked about the New Year's Eve party! Cassia, Amber, you are coming again, aren't you?"

"Of course," I said. "All of the police force will be there."

Alex leaned forward. "What am I missing?"

"Nothing," Gem said. "Because you'll be going, too."

"It's tradition for everyone to go to The Silver Star on New Year's Eve," I explained. "There's always a party, and it's very popular."

"There's no better place to be!" Gem said. "Promise you'll come."

Alex smiled. "I promise."

The volume suddenly seemed to rise on the TV, an eruption of noise, and I looked up. A crowd was filling the screen, jostling each other around the entrance to New London Crown Court. Two people were being led out by uniformed police officers -- Stellan Atkinson and Robbia Wells, the manager and accountant who'd been charged with the crime of conducting a sexual relationship with their subordinate or superior. A news crawl scrolled across the bottom of the screen. ATKINSON AND WELLS SENTENCED FOR LIFE.

The hairs on the back of my neck stood up, and my stomach tightened. It took me a second to realise that it was not a reaction to the news.

I picked up my weapon.

"Amber?" Alex said. "What is it?"

A window shattered in the flat. Cassia flinched. Gem screamed. Alex and I shot to our feet.

"Stay with Gem!" I yelled, and tore into the hallway.

A PRB was walking towards the bathroom, hefting its rifle. The door flew open, and a black blur shot out. A knife glinted.

"Freeze!" the PRB said.

Maxx shoved it back and came towards me. Everything happened so fast. I raised my gun, but I was too close, too slow, and the knife was already against my chest. Every part of me froze but my forefinger as it settled against the trigger. All I saw was the blade.

Then he was past me.

Turning, I tracked him down the hall with my pistol, but the PRB beat me to it. A rifle gunshot cracked the air. Maxx ducked down, almost stumbling, and bolted out the door.

Cassia appeared in the living room entrance. She hesitated for a split second, then ran after him.

"Cassia!" I yelled. "No!"

Counting on the PRBs for assistance now would be hopeless. Their orders were to protect Gem, and so they would stay.

It was just Cassia and me.

She reached the door just before it clicked into place and flung it open again. We ran through, her in front, me two steps behind.

The corridor was empty. The lobby was empty. Cassia had a good sprint on her, and she drew further ahead. Automatic doors slid open. She plunged into the darkness.

My heart kicked into a gallop. She would catch up with Maxx and try to tackle him so that he could be safely detained. But she wouldn't manage it. She wasn't trained for it. She'd get stabbed.

"Cassia!" I shot out the block, frantically scanning the darkness for her.

She was already on the road. Maxx had melted into the shadows.

And then she went down.

Something shiny winked in the lamplight as she skidded across the concrete on her knees. I ran towards her. "Cassia! Are you okay?"

She rocked back on her haunches, gingerly examining her hands. I stumbled to a halt beside her. Grazes ran over her palms, and her knees were bloodied and gritty.

"I'm okay," she said between deep breaths, standing up again.

My gaze was still on the floor. The shiny thing she'd tripped on winked at me.

A tabphone.

I fumbled in my pockets and found a clean tissue to pick it up with. When it was in my hands, I gave her my best glare. "What did you chase him for? He could have turned around and stabbed you!"

"I was the closest." Cassia shivered and pull her coat tight. "I wanted to help. And I wanted to protect Gem."

"But he was armed..." I sighed and shook my head, watching the stubborn expression I was familiar with settle across her features. "Ugh, never mind. I don't have time for a lecture. Come back inside."

We trooped back in, Cassia limping slowly. I slammed the front door behind us. "He got away!"

Alex appeared in the living room doorway. "Are you both okay?"

"Mostly." I herded my sister past him. "Cassia, sit. Alex, I want you to call this in."

"Right."

Gem was on the sofa, her legs uncurled and her hands tight over her knees. She was so pale that I thought she might faint.

"You're safe now," I said softly. "We freaked Maxx out. He won't come back. Cassia, don't leave her until I tell you to. I'll fetch a glass of water."

I went into the kitchen, clenching my hands until my nails cut into my palms. Gem was safe...but Maxx had escaped from us. Again.

Alex entered the kitchen behind me. He found a glass and filled it, so I rummaged through the cupboards until I found a chocolate bar. I thought Gem could do with more sugar.

My sergeant turned the tap off as I shut the cupboard. The sleeve of his jacket brushed against mine, but it might as well have been his naked skin, because a bolt of chemistry passed between us like static. I pulled away and met his eyes. Something simmered in the air between us.

He looked down and cleared his throat. "Well? What exactly happened?"

I turned around, fiddling with the chocolate bar. "Cassia and I chased after him, but she was faster than me. She'd almost caught up with him when she slipped on a tabphone."

Alex dredged out a pair of nitrile gloves from his pockets, and I handed the tabphone over to him. He tried to unlock it, but it didn't respond.

"There's a charging pad on the far counter," I said.

He took the tabphone over. "By the way, Dixon's coming, and he's bringing Inspector Flynn as backup. But I think we're more likely to get a lecture than we are to see Maxx again. Dixon sounded pissed that the guy we've been hunting all day showed his face and we didn't manage to arrest him."

***

Ky Dixon and Sebastian Flynn were accompanied by a handful of officers and several more PRBs, who passed us by in the hallway and got to work examining the bathroom, which had become a crime scene. Dixon herded us into the kitchen and shut the door.

Alex and I stood at the end of the room, as far away from him as possible. Sebastian leaned against the counters and shot us a sympathetic look.

Dixon folded his arms. "Are you both all right?"

"Yes, sir," I said.

"Good." His eyes narrowed. "In that case, you can explain how Maxx Ackerman managed to escape when you were in this flat with him."

"It was my fault, sir," I said. "I made Alex stay here with Gem instead of letting him come with me. He would have been fast enough to stop Maxx."

"Didn't you trust the PRBs to guard her?"

"No, sir! Six of them were patrolling the flat inside and out, yet Maxx still broke in."

Sebastian looked at Dixon. "With all due respect, sir, she makes a fair point."

Dixon glared at him.

There was a knock on the kitchen door, and Cassia entered the room. Sebastian straightened up, looking at her knees. "What have you done to yourself?"

"I tripped over." She turned to Dixon. "I just wanted to say that this is all my fault. I got in Amber's way."

His eyebrows rose. "You chased Maxx?"

She nodded.

"You're a pathologist, Cassia. You're supposed to look at dead bodies, not become one."

She hung her head, but I could see her fighting a smile. "Sorry."

"I give up with you lot." Dixon sighed and turned away. "I'm going to reorganise those PRBs. Make sure someone takes Gem's statement." He left, shutting the door behind him.

"Cassia, I told you to stay with Gem," I said. "First you try to capture a murderer for me, and now you're fighting my battles."

"That's what sisters are for. Anyway, there's an officer with her right now, so I came to fetch myself a drink."

"Forget that," Sebastian said. "Sit down and clean those grazes. You've got gravel in them."

Cassia hesitated.

He moved away from the counter and patted the surface. "Come on. You're a doctor. You should know better than this."

"All the patients I see are dead," she pointed out, but she pulled herself onto the counter anyway.

I filled a glass for her, and Sebastian grabbed a tea towel and ran it under the tap. While he cleaned her up, I turned to Alex. "How's the tabphone doing?"

He lifted it off the charging pad and tried turning it on. I went to him, and we watched the screen slowly flicker to life. The Castle Robotics logo unfurled across the dark space.

We waited.

Finally, the lock screen appeared. The owner's name was displayed in the top right-hand corner.

Daniel Castle.