Tony keeps the heat in his bedroom higher than any other room in the house. The others tease him, saying he only does it so he can sleep shirtless or perhaps in nothing at all, and he lets them, because he can't admit the truth.
His room needs to be warm enough that he doesn't need his comforter. A sheet, a light t-shirt, the arc reactor can shine through both of those, but its light can't break through the down comforter Pepper bought to bring out the warm red tones in the walls.
When Tony lies down in bed his mind is usually buzzing with equations, ideas, sometimes alcohol though the last one not as much anymore, but in the few moments before sleep overtakes him, everything goes silent.
Silent and dark.
Sometimes Tony jolts awake, because he can't handle the darkness. It reminds him of the hood over his eyes. He had been straining to see after the flash of the explosion and then hands grabbed him, voices spoke in a language he didn't understand, and a bag was shoved over his head, blocking out even the smallest hint of light.
It reminds him of having his head shoved beneath the water. There is no light to be found during torture. It reminds him of how dark the cave was when he found Yinsen's body. It reminds him of being alone, of the heavy responsibility of losing someone you care about, of worrying that none of it was going to be enough, and he would die as well.
His pulse pounds in his ears and his mouth is dry like he's going to throw up. He knows a cold sweat has broken out on his skin, and wonders where he is this time. Has his head just been pulled out of the water? Has he woken up strapped to a car battery? Is Yinsen dying in his arms?
And then the light of the arc reactor reminds him where he is. The soft blue light illuminates Steve's face, the long dark lashes, the lips that are curved into a smile even while he sleeps. Steve is the only one who knows why Tony keeps his room warm, but Steve knows a lot of things about Tony that no one else does.
Steve is easy to talk to, because he can keep a secret, because he gives Tony his full attention like nothing else in the world is important except for what Tony is saying, because while sometimes his eyes soften, filling with concern or because his lips tighten with anger there is never pity. But most of all, Steve is easy to talk to because he understands.
Tony puts Steve's hand on his hip, curls his body into Steve's, and feels safe.
The first time Steve spends the night in Tony's room, Tony asks if he wants him to turn the temperature down. Steve says no, because he's too polite to tell someone what their thermostat setting should be in their own room.
Steve wakes up sweating and with Tony's sheets wrapped around his feet from when he tried to kick them off.
The second time Steve spends the night in Tony's room, Tony changes the temperature. Steve doesn't say anything, because it's Tony's room so he can do whatever he pleases, but when he wakes up, Tony has his comforter wrapped around his waist, and he's shivering.
The third time Steve spends the night in Tony's room, he keeps Tony from changing the room settings. He tells Tony that he likes it warm which isn't a lie. Steve doesn't deal well with the cold anymore.
Every time Steve sleeps in Tony's room, Tony sleeps facing away from him, and it takes until the fifth time for Steve to figure it out. Tony is ashamed of the arc reactor, and he's afraid the light will keep Steve awake. Steve turns him so they're facing each other and wraps a firm arm around Tony's waist, pulling him close.
Sometimes it's disorienting to wake up to the room bathed in cool blue light. Steve's heart pauses, because everything is blue except for where it's dark, and he wonders if this is what it's like to be awake as you're frozen alive.
But then he feels warm breath against his cheek, the press of a thigh against his legs, and he remembers where he is. He traces the ring around the arc reactor, and he runs his thumb down Tony's jaw line.
On a bad night, he runs his hand down Tony's back until he's reassured that Tony is warm and breathing, and there is no ice in there room. There is only the two of them, their bodies intertwined, and Steve lets Tony's even breathing bring his back under control.