Disclaimer: I don't own anything related to Harry and co.
Sirius Black put his hand onto the door of the library in his ancestral home, located at 12 Grimmauld Place, only to freeze as if he'd been caught by a well placed Petrificus Totalus. The reason for his sudden immobility was not a full body bind however, but the noise which came from behind the door. It was a noise Sirius was rather familiar with, a decidedly feminine moan of pleasure. Sounds of this particular nature didn't usually make Sirius freeze, usually they made him grin rather smugly and continue with whatever it was he was doing, as he was usually the cause of the moans, not an eavesdropper.
There were only two people who could reasonably be moaning in his library on a Friday evening, Hermione Granger, who lived at Grimmauld Place with Sirius, Remus Lupin and Harry Potter, and Ginny Weasley, who didn't live there but spent so much time there with Harry that she might as well. In fact she would, but her mother wouldn't hear of it, and strongly disapproved of Hermione living with three unmarried men. Of this choice of two Ginny was ruled out since she was currently on a double date with Harry and Ron and his latest girlfriend.
That left the somewhat surprising conclusion that the female behind the door he was currently stood in front of must be Hermione. Although she had grown up and mellowed considerably in the years since the end of the war and her graduation from Hogwarts she was still fundamentally the same slightly overbearing bookworm she had been at thirteen, which made her an unlikely candidate for the kind of encounter which made her moan like that in a library.
"Oh Merlin, Remus, that's so good." Well, if the mews of pleasure had been surprising this was significantly more so. Sirius had suspected for a while that his oldest friend thought rather more of the lovely Miss Granger than he was letting on, but he never thought Remus would act on it. Unless of course Remus hadn't acted on it and Hermione was entertaining herself with thoughts of Remus, a hypothesis which quickly jumped into Sirius' somewhat gutter based mind.
The deep and most definitely male chuckle which followed her breathy statement quickly blew that theory out of the water.
Suddenly Sirius became aware that he was stood behind a door listening to his best friend and his godson's best friend doing whatever it was they were doing, which was a bit creepy whichever way you looked at it. He had two choices, he could leave them alone, or open the door and find out just what was going on. For reasons he couldn't explain, since he'd never thought of himself as having voyeuristic tendencies, he chose option two and opened the door.
The sight that greeted him was not what he expected. Remus and Hermione were sharing the couch by the fireplace, and on the coffee table in front of them was a partially eaten bar of Honeydukes chocolate.
At the sound of the door both occupants of the room turned towards him. Realising that he needed a reason for walking into the library, and as the truth wasn't really an option Sirius tried to remember why he had been at the door in the first place.
"Alright you two? I was just wondering if you fancied going out for a drink, since its Friday and all." He hoped he didn't sound as confused and embarrassed as he felt.
"Sounds good to me, coming Hermione?" asked Remus. Hermione smiled at the men but shook her head.
"No thanks, I think I'll stay here and finish my book. Thanks though. And thanks for the chocolate Remus."
"If you're sure?" Hermione nodded. "You can keep the chocolate for company then." Remus smiled as he walked towards Sirius. "It's the new flavour from Honeydukes," he said to Sirius as they left.
Chocolate, thought Sirius, I should've known it'd be something innocent like that with those two. He was so caught up in his thoughts that he didn't notice the scrap of black lacy material just peeking out from under the sofa, or that Hermione's shirt was buttoned up wrong.