It takes a while for him to notice her slipping into his life, so when he finally does she's sleeping on his couch at 5am. Reeking of firewhiskey and something disgustingly sweet that he can't place.
As he moves towards her petite form on his old and worn-out couch he almost trips on one of her boots that she's thrown on the floor. When he looks around for the other one, he finds that she didn't even get to pull it off before she fell asleep.
He lets her sleep of her obvious intoxication, just covers her with a blanket before going back to sleep.
x
Sirius and Marlene are not friends, not at all.
They talk, not often but they do, about dumb things like James' ugly sweater or why gryffindor shouldn't have won the house cup that year or another.
They hang out with the same people, she's Lily's best friend and he's James'. But every time they're all supposed to get together, her seat's empty. If someone asks Evans she usually just sighs. Sirius knows how hard it is to admit their friend is out drinking themselves unrecognizable instead of meeting her friends.
Marlene and James are friends too, former quidditch captains and all. Maybe that's why Marlene has "moved" into Sirius apartment, he is after all her friend's best friend and friend's do favors, right?
x
Marlene disappears for a week and if she were someone else, like Lily, he would never be able to sleep at night. He would bite his nails to the core and search the whole world. Twice.
It takes him three days to notice the lack of cigarette smoke in the headquarters, the lack of her old jacket lying on the floor in his apartment, the lack of her curses filling the tense silence during the meetings.
He forget's to ask some of her friends where she's gone off to, he's too busy with the order, with James and Lily, life takes over and she's somewhere in the back of his head.
Once, when the night is still young and there's no trace of her and he's got way too much firewhiskey in him, he contemplates her leaving them. Maybe she took her broom and flew away, she's good at that, pretending to be a bird in the wind.
And then he remembers her curses and angry screams and how could he think she would be the first to leave? Maybe she's not a true gryffindor but there's still bravery running through her veins. His anger over her transforms into anger against himself and he falls asleep angry and wakes angry. Maybe he hates her, she wouldn't be the first.
x
She returns after eight days, crawls into his apartment in the middle of the night, leaves before sunrise. The couch still smells like her cigarettes when he wakes up. He sips into the scent of her and let's out a sigh of relief, then he almost pours coffee into a second cup just for her and the anger comes back.
He storms into headquarters ready to scream at her, for moving into his apartment, for poisoning his couch with her smoke, for making him worry about her, for slipping into his life.
She turns her head towards him when he slams the door open, and she's unrecognizable. Her skin is so pale and there's purple marks on her neck and throat, there's a long gash above her eyebrow.
"What have you done?" he asks and curses himself for being so dumb. Someone doesn't run away to Paris during a war, they either get killed or caught and used as a bird in a cage.
"I escaped" she whispers back, and maybe that's enough. Maybe he doesn't need to know how they got to her or how they treated her. He just needs to know that she's back, that she'l still be there on his couch when he wakes from nightmares. His Marlene won't disappear, she'll be right back with a lit cigarette dangling from her lips and an amazing story to tell.
X
The day she dies he realizes something, when she slipped into his life she never intended to leave.
(He still wakes up sometimes, twelve years and an eternity later, and swears he can feel the smell of her cigarettes creeping trough the walls)