A/N: I usually post my fics on AO3 because they're too explicit for FF's guidelines, but this fic is mostly gen, so I decided to cross-post. This is part of an ongoing AU in which Matt Casey and Kelly Severide are in a long-term polyamorous relationship, Severide has been in a relationship with Jeff Clarke for about four months, and Leslie Shay did not die in the arson at the end of season 2 but did sustain a TBI and a spinal cord injury. For more, you can track me down on AO3 as "hosannachicago" and read the rest of my fics.

Enjoy!


"Engine 51, Truck 81, Squad 3, Ambulance 61, structure fire…"

It started out almost like any other call. Chief Boden was out on leave to be with his wife and newborn son at the hospital, but Kelly and Casey had handled plenty of fires without him before. Squad 3 arrived at the building full of storage units seconds before Truck 81, so Kelly took command of the scene. It was going to be a pain in the ass to check every one of those units, but the good news was that the fire would probably be easy to contain.

Herrmann found the fire in unit 208, and Cruz started cutting the door to get them in. The rest of Truck stood back, ready to jump into action once Cruz got through. Kelly hovered at Cruz's shoulder, carefully watching as the interior of the unit was gradually revealed.

"Whoa!" he yelled, almost before he consciously registered that he'd heard something strange. He stepped forward, stopping Cruz to take a closer look inside. "Whoa, whoa!"

Cruz stopped cutting, and Kelly cautiously peeled back a section of the metal door. The high-pitched whistling grew louder, and he took in the sight of a propane tank and gas cans scattered around the room.

"Hey, propane tank!" he yelled to Truck. "Get back!"

The flames hit the tank, and a fireball shot through the opening, nearly blasting him in the face. Kelly hit the ground, shielding his eyes. When he turned to face the others, he found them gawking, almost motionless, just a few yards down the hall.

"Hey, get back!" he yelled again, realizing only he knew how quickly the unit could go up. "This place could blow any second – get back, all of you!"

Casey confirmed his order, and the rest of Truck finally backed away. Dawson passed him her silver bullet as she left, and Casey stayed behind to help him knock down the flames. Working together, they were able to extinguish the fire before it got any more out of hand. As they did, Kelly took in some of the materials on the shelves – fertilizer, brake fluid, chlorine, antifreeze, propane...

Shit. If you could start a fire with it, it was there.

He stuck around for overhaul, despite Casey's offer to have Truck handle it. When a ball of flames came inches from blasting him in the face, he took the investigation personally.

"Looks like this pile of boxes knocked this can over. Vegetable oil seeped into the rags," Casey observed, pointing it out to Dawson.

Kelly tuned them out while they discussed how the fire started. He had bigger questions.

"Whole boxes of brake fluid, a dozen bags of cat litter, and chlorine powder. That's not what most people keep in their storage lockers," he observed. He was sure of it now. "This looks like the stockpile of an arsonist."

"Alright," Casey agreed. "We'll get AI in here to have a look."

While they talked, Dawson wandered over to a table on the other side of the room. "Hey, guys?"

She held up a newspaper clipping, and Kelly noticed at least half a dozen more on the table. The page in Dawson's hand was partially blackened from the fire, but Kelly was able to recognize a photo of the warehouse where Shay and Mills were hurt.

The three of them stared at each other, and he saw his own shock reflected on the other two faces.

"What the…?" Casey trailed off, picking up another clipping. It was from a different fire, one he didn't recognize on first glance.

"It – It wasn't arson," Kelly said hesitantly, unable to even begin to comprehend what that would mean. "It…?"

Dawson shook her head sharply. "No. I mean, there were no signs, right?"

Kelly shrugged helplessly, realizing he had no clue. "I didn't think… but I mean, I didn't do the overhaul – Case?"

Casey looked up at them, holding two of the other news stories in his hands. "I – I didn't do it either," he admitted. "It seemed cut and dry, with the squatters, so we all just went to the hospital as soon as the fire was out. Engine stayed to clean up. But – look. These are all from different fires. All over the city, going back years."

"Maybe – maybe he's just an enthusiast," Dawson weakly attempted. "Collecting stories – it doesn't have to mean… Peter and Shay…"

Feeling lightheaded, Kelly leaned back against the wall. "Okay… Okay, yeah, you're right, it might be nothing."

The expressions on their faces made it clear. None of them believed that for a second.

What the hell?