The bunker’s ancient heating system gave up sometime after midnight. One minute the air was tolerable, the next it felt like someone had opened a freezer door and left it that way. You woke up shivering in your room, teeth chattering, the thin blanket you’d fallen asleep under suddenly useless.

Dean’s room was closer to the working vents, so he was probably fine, snoring through the apocalypse like always. Sam’s room, though… Sam’s room still had heat. You’d overheard him mention it to Dean earlier, something about the ductwork being rerouted years ago when he’d needed the extra warmth after a bad case of hypothermia.

You stood in the hallway for a solid five minutes in socked feet, arms wrapped around yourself, debating. It wasn’t a big deal. You’d just ask to crash on his floor. Or the chair. Or… somewhere that wasn’t freezing to death.

You knocked softly. Nothing. Knocked again, a little louder. “Sam?”

The door opened almost immediately, like he’d been standing on the other side. He was in a gray T-shirt and flannel pajama pants, hair messy from sleep he clearly hadn’t been getting. The room behind him was warm, golden lamplight, the faint scent of cedar and gun oil and something that was just him.

“Hey,” he said, voice low and rough. “You okay?”

“It’s… arctic out here,” you managed through chattering teeth. “Dean’s snoring like a chainsaw and hogging all the heat. Your room still works, right?”

He hesitated, just for a second, then stepped aside. “Yeah. Come in.”

You slipped past him, clutching the blanket you’d dragged from your bed like a sad cape. The difference was instant, like walking into summer. You let out a shaky breath of relief.

Sam closed the door quietly behind you. “You can take the bed,” he said, already moving toward the small armchair in the corner. “I’ll—”

“No.” The word came out sharper than you meant. “I’m not kicking you out of your own bed, Sam.”

He rubbed the back of his neck, not quite looking at you. “There’s plenty of room. It’s… big enough.”

It was. The bed was huge, one of the few decent things the Men of Letters had apparently believed in. You both knew it. You both pretended you didn’t.

You nodded once, throat tight. “Okay.”

He turned off the lamp. The room fell into darkness lit only by the soft glow of the bunker’s emergency strips along the floor. You climbed in on the left side, the one closest to the door, always. He took the right, leaving a careful, aching foot of space between you.

For a long time, neither of you moved. You lay on your back, staring at the ceiling, hyper-aware of every breath he took, every shift of the mattress. The warmth was bliss, but it wasn’t the cold keeping you awake anymore.

You weren’t sure when you fell asleep.

You woke slowly, warmth everywhere, front and back. Your face was pressed into the hollow of a broad chest, one heavy arm locked around your waist, a long leg thrown over yours like he was afraid you’d slip away in the night. Sam’s heartbeat was steady under your cheek, slow and deep, his breath stirring your hair.