What goes bump in the night.
Inspired by the 31 Days theme for Halloween 2006. Set vaguely after Book Five, with spoilers for its end.
In the year following his escape from Azkaban and his liberation at the hands of Albus Dumbledore and his nephew Harry Potter, it had become Sirius Black's habit to steal away to Remus Lupin's cottage somewhere in the British countryside. He would, as Padfoot, scratch his toenails against the door until Remus let him in, and take great pleasure in slobbering all over his lover's face as a dog before reverting to proper form and engaging him in human conversation. He would never stay long unless Remus touched his hand and said, in his quaint way, how the weather was always cold at night where they were. In those cases they'd use each other as blankets and Sirius would leave the next evening.
When Dumbledore established the Order of the Phoenix Sirius had been the first to answer only to end up a prisoner in his own family home for his enthusiasm. It was Remus' turn to do the knocking (scratching) at Sirius' door to join him there for as much as he could, and tolerated the tough love and rough sex and growing pains of a godfather concerned for the only living memory he had of their dear friends. Sometimes he would apologize. Sirius always told him not to.
In the next year, Lupin returned to his cottage. Sometimes, in the middle of the night, he'd wake up thinking he heard a dog scratching at the door.