the_debt_of_time

When Remus did not make an appearance, Sirius realised that the horrible smell of what
he assumed was Wolfsbane Potion must have overpowered any other scents, for which he
was grateful.
"Ah, Severus. Thanks very much. Could you leave it here on the desk for me? I was
just showing Harry my grindylow."
"Fascinating," Snape drawled. "You should drink that directly, Lupin."
Git, Sirius thought bitterly.
"Yes, yes, I will," Remus replied.
"I made an entire cauldron," Snape continued. "If you need more."
"Thanks very much, Severus."
"Not at all," Snape said before walking out of the room, causing Padfoot to duck
deeper inside the alcove to wait for him to pass by.
"Professor Snape has very kindly concocted a potion for me," he heard Remus say.
"I have never been much of a potion-brewer, and this one is particularly complex. Pity
sugar makes it useless."
Sirius could almost grin as he pictured him drinking the nasty potion. There had
been plenty of jokes about it growing up. Once, Sirius had borrowed Lily's Muggle camera
to take still photographs of Remus's face while drinking the Wolfsbane. The only other
person who found them funny had been James. Mia had thrown the empty goblet at his
head over it.
While Harry and Remus kept one another occupied, Sirius crept away soundlessly.
He refamiliarised himself with the old passageways, evading a few wandering students and
silently amusing himself when the moving shadow his body created frightened a pair of
snogging teenagers out of an alcove. He waited patiently until the students made their way
down to the Great Hall for dinner before he darted through the corridors and up the
staircase, until he found himself standing before a very familiar painting.
Fuck. The portrait. How had he forgotten about the portrait? Overwhelmed by anger,
Sirius shifted into human form and glared at the Fat Lady just as she opened her eyes.
"Open."
"Oh, I don't think so!" the Fat Lady shouted. "I remember you, young man, and I
know what you've done since leaving this place!"
"Open!" Sirius snarled, his teeth clenched tight.