Sirius twitches in his sleep now. He shivers and curls up small. He mutters, groans, whimpers, sometimes sobs, sometimes makes noises Remus has no name for.
In the mornings he looks sickly and exhausted, but relieved. As if day's a thing he can't believe in and never dares hope to see. He doesn't talk about his dreams.
Remus mostly lies awake, these nights. Sleeping would be abandonment, leaving Sirius in another dark prison. An expiation's needed, payment for every night Remus slept without thinking of Azkaban.
"I'm here," he whispers while Sirius trembles through nightmares. Unhearing, helpless. "You're not alone."