Aaron walked out of the BAU building, the weight of the day sitting lighter on his shoulders than usual. The sun was setting, casting long shadows over the Quantico parking lot as he casually pushed a black stroller down the pavement. Inside, nestled with a stuffed lion in one hand and his sippy cup in the other, was his two-year-old son, Jamie—bright-eyed, curly-haired, and currently making soft babbling noises to himself.

Hotch had one hand on the stroller and the other holding his phone to his ear, his brow furrowed in concentration.

“JJ, Kai’s at work, and—I think Jamie needs a change. How do you change a diaper again?”

There was a pause on the other end before JJ’s voice came through, clearly trying not to laugh. “Wait—you don’t know?”

Aaron sighed, glancing down as Jamie squirmed slightly. “I mean… I’ve done it. A few times. But Kai usually handles this kind of thing. I’ve been on the road most of the past year.”

Jamie let out a soft grunt, and a suspicious odor began to rise from the stroller.

“Yeah,” Aaron muttered. “It’s happening. It’s definitely happening.”

JJ was laughing now. “There are videos online, Hotch. You're the Unit Chief of the BAU—you’ve stared down serial killers. You can handle a diaper.”

He hung up and slid his phone into his pocket with a sigh, stopping beside the car. He crouched beside the stroller and pulled out his phone again, tapping through YouTube.

A moment later, a bright, overly enthusiastic voice was echoing from his screen: “Step one: always make sure you have all your supplies before beginning!”

Hotch frowned. “Supplies. Right.”

He opened the diaper bag Kai had packed—thank God—and laid out the essentials on the back seat. Wipes. Diapers. Baby powder. It looked like a mini tactical kit, and for some reason, that comforted him.

He gently lifted Jamie from the stroller and laid him carefully on the padded seat, trying not to gag as he undid the soiled diaper.

Jamie giggled.

“You think this is funny?” Hotch asked dryly. “You’re lucky you’re cute.”

Jamie giggled louder, kicking his legs.

Aaron wrinkled his nose as he worked. “You smell, buddy. Maybe it’s ’cause you poop too much. Hm?” he said, his voice light but edged with faux-seriousness.

Jamie just blinked at him innocently and pointed at his lion, clearly unfazed.

Hotch chuckled under his breath as he tossed the diaper into a trash bag and wiped Jamie clean like he was disarming a bomb. “One day, you’re gonna repay me for this. And it better be in coffee.”

By the time Kai called to check in on them, Jamie was freshly diapered, happily munching on a rice cake, and Aaron was sitting on the curb next to the stroller, looking mildly traumatized but strangely proud.

“Operation Diaper: successful,” he muttered, then added, “Don’t tell Morgan.”