The water tower reeked of stale rain and pigeon droppings, the air heavy with damp rot. Gravel crunched under Cap's boots as he vaulted over the rooftop's edge, shield raised, eyes scanning for threats. Rex followed close, hands empty but twitching, ready to form machines if needed. The city skyline flickered in the distance, lights stuttering like a failing pulse.
Van Kleiss stood with his back to the rusted tank, holding a cobbled-together device—pipes, wires, and a strange, pulsing material that wasn't quite metal. It thudded once, low and ominous, like a heartbeat from the machine itself. "Hello, Captain," he said, voice smooth and mocking. "You're quite the camera magnet, aren't you?"
Cap didn't respond, moving left to cut off Kleiss's escape route. His boots scraped the gravel, shield angled to block any sudden moves. Kleiss just smiled, keeping the tank between them like a chess player holding a pawn.
Rex stepped right, circling, his eyes locked on the device. "That handshake you sent to Stark Tower? Real cute trick," he said, voice sharp with anger. "Trying to show off?"
"I wanted Stark's attention," Kleiss replied, tapping the device lightly. "He's so easily distracted, that one. This little toy? It rides the water lines, humming to the city. Softly. Far-reaching. Every sink, every faucet—mine."
Cap hurled his shield, fast and precise. Black tar surged from the wall, swelling to slow the shield's spin, but it punched through, clipping the device's edge. The hum faltered, a glitch in its rhythm.
Kleiss's eyes flashed with irritation, his calm cracking for a split second. He flicked a finger, and black spikes erupted from the gravel. Cap blocked three with his shield, the impacts ringing out, but a fourth grazed his thigh, tearing fabric. He didn't even flinch, advancing steadily.
Rex charged, boots pounding, closing the gap fast. Kleiss moved like smoke, sliding out of reach. The device hit the ground with a clatter. Rex dove, slamming his palm onto it. A jolt hit him—not electricity, but a coded instruction, sharp and invasive. He sensed its target: Substation 14, the city's power grid, ready to spread chaos. Gritting his teeth, he crushed the device, grinding it into sparks and twisted metal.
Kleiss's smile tightened, his voice cold. "Bad manners, Rex."
Rex swung a fist, hard and fast. Kleiss raised a slab of black stone from the ground to block it, stepping back without a scratch. "Better," he taunted, his coat fluttering slightly.
Drones buzzed overhead—NYPD, not Stark's. Their lights swept the roof, and a loudspeaker blared, "Hands up, on the roof! Show 'em now!"
Kleiss glanced up, unbothered, then stepped backward off the edge. Rex lunged, catching a glimpse of a black ramp forming midair, guiding Kleiss into the alley below. He was gone before their boots hit the gravel again.
Cap took a sharp breath, already moving. "We're not done. We keep after him."
Rex scanned the skyline, where lights flickered in a jagged line, like someone dragged a finger through the city's power. "He's always one step ahead," he said, voice tight with frustration. "He's playing us, Cap."
"Then we play smarter," Cap said, grabbing his shield from the tar. "Let's move."
Across Manhattan, Natasha and Tony dropped into the substation yard, boots hitting the concrete with a thud. Transformers hummed in rows, but a second, off-key note cut through the sound, like a glitch in the system.
"Talk to me, Nat," Tony said, his suit's HUD scanning the yard. "What're we looking at?"
"Pulses in the A bank," Natasha said, checking a handheld device, its screen glowing faintly. "He's seeded the sync system, messing with the grid's rhythm."
"Where's it coming from?" Tony asked, repulsors glowing as he hovered an inch off the ground.
"Control house," she said, nodding toward a low brick building with a heavy steel door. "It's inside, spreading fast."
They hit the door, Tony blasting the lock with a quick repulsor shot. The air inside was thick with dust and the tang of hot metal. Control panels blinked nonsense, lights flashing in no pattern. A black sheen crept over the breaker boxes, slick like mold but moving with purpose.
Tony grimaced, scanning the room. "I hate mold. Burn it or cut it?"
"Neither," Natasha said, pulling two small charges from her belt. "We blow it. Directed blasts, minimal shrapnel. Keeps the grid intact."
"Love minimal," Tony said, spinning up a shield plate from his suit's forearm. "Let's make it quick."
Spider-Man vaulted the outer fence, landing on the control house ceiling with a soft thump. He stuck there, peering down. "What's up? Creepy guy leave you a love note or two?"
"Couple of 'em," Tony said, pointing at a seam where the black was spreading across a panel. "Web that shut, Spidey. Keep it from creeping any farther."
"On it!" Spider-Man fired webs, sealing the seam tight with a quick flick of his wrists. "This stuff's grosser than my gym locker, and that's saying something."
Natasha set the charges in two corners, her movements precise. "Three. Two."
Tony threw his shield plate, covering them. The charges detonated with a sharp bang. Panels popped like soda cans, and the black sludge slumped to the floor, lifeless, smoking faintly.
Friday's voice crackled in Tony's ear. "Grid draw stabilizing, sir. For now."
Tony didn't relax, his HUD still scanning. "He's not done," he said. "He'll hit again, probably harder."
"He will," Natasha agreed, pocketing the spent remotes. "He's testing us, seeing how fast we can react."
"Then we need to be faster," Tony said, already running diagnostics on the grid. "This guy's playing chess, and we're stuck playing catch-up."
Spider-Man dropped to the floor, webbing another creeping patch. "So, what's his next move? More creepy mold? Or something worse?"
"Worse," Natasha said, her voice flat. "He's not here for small wins."
Before Tony could respond, Stark Tower's alarms screamed through his comms. A distant thud shook the ground, rattling the control house windows. Friday's voice cut in, urgent. "Mr. Stark, intrusions detected in lobby, mezzanine, and service core. Source: nanite constructs. Quantity escalating rapidly."
Spider-Man's head whipped around. "Your house, Tony! He's hitting your house!"
"Stay with Romanoff," Tony ordered, his suit powering up as he lifted off. "Keep this yard clean. Don't let anything spread."
"Got it," Spidey said, webbing another seam shut. "Go be Batman or whatever! We'll hold the fort here."
Tony rocketed toward Stark Tower, its lights cutting through the night like a beacon. The lobby doors were wide open, black smoke pouring in, weaving around the automated turrets' laser fire. The nanites adapted in seconds, dodging and reshaping like they were learning on the fly.
Tony hit the swarm like a missile, repulsors blazing full force. "Not in my house!" he shouted, blasting a wave of nanites into ash. "You picked the wrong tower to mess with, pal!"
Back at the substation, Spider-Man swung around the yard, webbing up every black patch he could find. "This is like playing whack-a-mole with evil slime," he muttered. "Nat, you got any more of those bombs?"
"Fresh out," Natasha said, scanning the yard for stragglers. "We need to lock this place down before it spreads to another grid."