Who: Sirius and Remus (and Narcissa if she'd like to drop in) When: March 22 Where: Remus's house What: Sirius wants to talk to his friend about stuff.
Sirius, despite his penchant for trouble making and being a general nuisance, was lonely. James was nowhere to be found most of the time and Remus set up shop miles and miles away. Sooner or later Sirius knew he'd run out of petrol and his bike would be useless unless he found a way to get more. He wouldn't be able to make day trips out to see Remus or visit anyone who might be out of the city and needed help.
To say that he was annoyed when Remus went back to his parents' house would be an understatement. His having Narcissa in tow irritated him further. He couldn't care less what they were doing together, just that Remus seemed insistent on being as far away from everybody else as he could. He and Sirius had done little but argue and right now Sirius wanted to talk. He didn't know what about, but he wanted one of his friends. Even if it seemed to Sirius that Remus wasn't interested.
He got to Remus' doorstep in the middle of the night. He was determined to show up at an inconvenient time. He knocked on the front door loudly and waited.