Regulus' smile falters but only for a split-second. Then he's nodding, leaning down to kiss the top of Sirius' head affectionately. "I'll get plenty of rest, I promise. You get rest too, okay? You need to focus on getting better."

He needs to go. He needs to hurry. He doesn't want to but he squeezes Sirius' hand again, one last time, before taking a step back. "I'll go and let you rest now, okay? I love you, Sirius."

It's soft but readily audible for his brother to hear. Once he finishes with his goodbye he leaves the room and looks around once he shuts the door. There are a couple Healers rushing to the door he'd closed on Remus.

"Fuck."

It's not graceful but he takes off, tearing down the corridor with his cloak fluttering behind him. It's late enough not many people are around so it's easy, but he makes sure he's out of sight and gone before they can get Remus free.