What a small world you've made for yourself, Lupin.
He's not just thinking of the basement, a shallow stone basin under the house to house old pipes and the occasional werewolf. It's wet and rank much of the year, freezing in the Winter, and drives up the rent, but he wasn't paying for it. What he did scrape together for was the sturdy door atop the steps, it's lock. There's no point warding a door he could splinter by paw.
A good cage has always been invaluable to him.
No matter what kind of cage it is, he thinks with a sigh, too exhausted to hurt anymore, to do more than peel off his jumper and set it in the bin, settled out of the ways by a washing machine he uses more to pass time than keep his clothes clean (though, the way most of his shirts look, another scourgify would unravel them). The closer the sun gets to the horizon, the more the room agitates him, the more the old smell of bleach becomes overwhelming, burning, but bleach is better than the reek of blood and piss. After a moment's consideration, he moves the bin onto the washer--he'd once woken to find his clothes soaked in urine, and he wants to take that chance again about as much as he wants to examine the meaning of it.
He remembers how his friends had laughed when he'd told them, see, even you know those trousers were absolute rags, and maybe he isn't so exhausted he can't grit his teeth, think, Sirius Black has ruined my life in a disgustingly petty way, and wonder if it's even worth locking himself up anymore. If there's anything to hide from or protect, now that James and Lily are dead, now that Peter, poor fucking Peter--
Remus can only wonder what Sirius had planned for him, wonder if there's some ego in assuming he'd be next, if it meant something that Sirius saved him for last or just happened upon Peter first, but he can't imagine the broken man they dragged off to Azkaban had any intention of letting him outlive them. And wouldn't it have been better if he hadn't, if Sirius had evaded arrest just long enough to finish the job. If he'd done something more than open that cage's door in the worst possible way.
It's all right, Remus tells himself, though it couldn't possibly be less all right: he can go from one cage to another, strip down to his pants in the chilly basement and bolt the door, set his wand on the narrow sill of a painted-over window.
He nearly falls down the steps when it takes him, the first jolt of the change when his vertebrae split to multiply, when his eyes itch and he's temporarily blind, pupils changing shape, irises reflecting new colors. When everything grows an edge and gets just a little bit feral, and he's halved--and one half wants Sirius locked down in here with him, wants two dogs snapping at each others' throat, and the other just wants Padfoot, Prongs, Wormtail--
and then he's whole again, and he just wants to bite.
- - -
There is honestly nothing so terrifying as waking from a transformation outside. He's just glad he wasn't using a cage any more, because outside in a cage plus naked and bloody would just be a step too far.
Before Hogwarts, before the Shrieking Shack, his parents hadn't any choice but to lock him up like that, to tell the neighbors they occasionally fostered dogs and apologize for the noise, and he'd been so young, he hadn't always understood why it was happening but he understood the look on his mother's face when they locked the door, he understood, in the lingering moments when he came out of it, the amazing smell of her skin and hair when she gathered him up and let him press his face into her throat, more like a puppy than a boy. And he misses that so fiercely right now, with no one to cleave himself to in the heady, horrible moments--
only it's not, really, he feels surprisingly fine, blessedly ordinary and small, for all the confusion, the heat and the usual bites. Everything is muted, almost dull, as if he'd leapt forward through the month to the new moon. Humid air steams from his mouth but has no specific taste; his senses only have room for Merlin's balls it is so bloody warm as he crosses sandy earth to his clothes bin, praying he's been stockpiling dirty socks in it as he picks out his trousers and drags them on. For a moment, he wonders if he's apparated, but a muttered charm has his stomach sinking and his gaze casting about for where his wand might be in the jungle that replaced his basement, when it fails to ease the sting of his scrapes.
Maybe he's just too tired to get the right inflection, and he thinks wryly of an old Muggle story, a man lost in the wilderness who freezes trying to build a fire. And his dog trotted off to find another master in the end, unmoved by his death; Remus huffs an irritated chuckle, damned if he'll follow that line of thought, when nobody is going to freeze to death in this weather. He finds his scuffed old boots shoved in the bin, atop the clothes. His hands, though torn, manage them with relative ease, and he spares the wounds no more attention than it takes to wonder if they're cursed bites or mundane wear-and-tear from the walls.
It's something he's used to: waking up in a forest with nothing but his laundry, not so much.