Snape stood in the doorway, looking down at the narrow bed that filled the room, and at the warm and relaxed sprawl of Al, his body stretched across the bed, filling the room, for once as unselfconscious as a drowsing cat.
For all his experience with casting Fidelius for himself, this was the very first time Snape had served as Secret-Keeper for someone else's Fidelius.
He could feel a strange, new awareness - of the house and the Fidelius-Caster's magic - seeping into his bones and his magical core. If he concentrated intensely, he could feel the way the floorboards expanded in the warmth of the sunlight that bathed Al's sprawled limbs.
He could feel the weight of Al's bed, and the books that entirely filled the space beneath it. He could feel the way the floorboard bowed under his own feet.
Perhaps he was deceiving himself, but he swore he could almost feel the swirl of air and sunlit dustmotes as Al breathed heavily in his sleep.
Snape couldn't have said what drove him, but the warm and beguiling weight of the invitation was palpable all the same.
Silently, he shrugged out of his robes, allowed them to slip off his narrow shoulders and drape along the bare floorboards.
Silently he knelt, drew the covers back, stretched out beside Al. His body and his magic were deeply drained by the intensity of teaching Al the Fidelius, participating in his casting, then immediately afterwards acting as his Secret-Keeper.
But the weariness in his magical core had the glow of satisfaction in a job well done, his body had the warm ache of a race well run. Softly he stretched out, his scrawny body just fitting in the narrow space beside Al in his single bed.
He draped one arm around Al's waist, sighed a slow, sated sigh, and slept, secure in the knowledge that Al's new house was as secure as his own knowledge of the Fidelius could make it.