MEXØ Prime pushed open the front door of the four-story headquarters and stepped into the dark. Green light strips flickered on along the walls. Prime wanted one thing more than anything: a real squad, humans and robots and drones building great things side by side. But right now the squad was small. Just Prime, a plush robot-dog named Robo, and three drones humming overhead. The big adventure was over. The HQ was empty. Prime had to make it feel like home. Robo bounced past on four fluffy paws, his neon-green crown logo glowing on his chest. His pink tongue hung out. "We made it! Can we play now? Please?" He skidded across the black floor and crashed into a wall. He looked up, grinning, unhurt. Prime laughed and pointed a glowing green hand at the stairs. "Deal. But we check every floor first." The drones spread out, scanning. Prime climbed. The first floor held command screens, still dark. The second floor had racing chairs and giant monitors. Prime slapped a wall panel. The whole gaming floor woke up. Screens lit green. Speakers thumped. Robo howled with joy and jumped into a chair. They climbed higher. On the third floor, Prime found the MEXØ command center. One console blinked, waiting. Prime pressed a palm to the scanner. The system booted, showing camera feeds of every room. Everything looked safe. "Good," Prime said. "Now we can breathe." The top floor was cozy. Soft couches, warm lamps, a window across the whole wall. The three drones settled into a charging dock like tired birds. Robo curled against Prime's leg and yawned. For the first time, the HQ felt alive. Prime rested a hand on Robo's fluffy head. "This is the start," Prime said quietly. "We build the squad from here." Then the lights changed. Every green strip in the building flared white, then blazed a deep, unfamiliar green. It was not the HQ's usual color. It pulsed like a heartbeat. The command console upstairs screamed an alert. Prime ran to the wall screen. A signal was climbing the building's own network, floor by floor, taking control as it went. Robo pressed against Prime, ears flat. "That's not us, right? Tell me that's not us." "It's not us," Prime said. The drones lifted off the dock, spinning, confused, following commands Prime hadn't given. On the big window, the outside world glowed too. Far below, snow-crusted branches shifted in the strange light. Something tall stood in the yard, frost-laced and watching, its blue eyes bright. A living tree, wrapped in winter, staring up at them. The signal wasn't a message. It was a door, and someone had just opened it inside Prime's own home. The HQ locks clicked shut, one floor at a time, sealing them in. Prime's green eyes narrowed. The squad had a home now. And already, something wanted it.

The doors clicked shut on every floor. MEXØ Prime stood at the command console, watching the strange signal crawl through the building. Prime's glowing green hands slapped the screen. Nothing answered. The controls were locked. Prime tried a voice command, then a manual override. Both failed. "It kicked me out of my own home," Prime said. The three drones spun in tight circles above, obeying orders Prime had never given. Robo pressed against Prime's leg, ears flat. His pink tongue was gone. "We're stuck? Really stuck?" He scratched at the sealed door with one fluffy paw. It didn't budge. Down in the yard, the frost-covered tree creature turned its head. Its blue eyes fixed on the window. Prime felt cold, even inside. "The signal came through the network," Prime said. "So the network is the way out." Prime knelt and pried open a floor panel near the console. Wires glowed underneath. The signal traveled these wires to reach the door locks. If Prime could cut the right one, the locks would lose their new master. But which wire? Prime traced the pulsing green light with a finger. One cable throbbed harder than the rest, feeding straight into the door controls. "That one," Prime said. Robo whimpered. "What if it's the wrong one?" "Then the doors stay shut and it wins." Prime gripped the cable. The drones dove suddenly, driven by the signal, aiming for Prime's hands. Robo barked and leaped, snapping his plush jaws at the lead drone. He knocked it off course. "Go, go, do it!" Robo yelled, tumbling across the floor. Prime yanked the cable free. Sparks jumped. The console screamed, then went dark. Every green light in the building flickered. For one long second, nothing moved. Then the locks thumped, all at once. Sealed doors slid open on every floor. The drones dropped from the air and clattered to the ground, dead and silent. Robo scrambled up and shook himself. "You did it! The doors!" He raced through the open doorway and back, tail whipping. Prime stood slowly, breathing hard. The trap was broken. They could move again. But the dark console gave Prime no camera feeds, no controls, no drones. Cutting the wire had killed the whole system, not just the invader. Prime looked at the three fallen drones on the floor. They had been part of the squad. Now they lay still. Worse, the front door of the headquarters now hung wide open at the bottom of the building. Prime crossed to the window and looked down. The yard was empty. The frost-covered tree creature was gone. Prime scanned the dark stairwell below. Wet footprints, rimmed with ice, marked the bottom steps. The thing wasn't in the yard anymore. It was inside, climbing, and Prime had no cameras left to find it.