Sirius waited quietly in the wild hedges near the castle, the winter night air whispering frostily through his fur. Tonight was the night he was finally going to kill Peter.

It wasn't until at least one in the morning that he heard it: a quiet mrrow coming from behind him, followed by an earthy whiff of cat scent. He turned to find a massive ginger feline picking his way through the hedges towards him—Crookshanks. In his mouth he held a tightly-rolled scrap of parchment, which he laid at Sirius's feet.

Sirius tilted his head at the cat, whining softly. It had taken him months to work his way into his confidence, but now Crookshanks was his closest ally at Hogwarts. Crookshanks knew what Peter was, too, and Sirius had let him know in the way only animals could communicate that the two of them were after the same rat. So now Crookshanks was helping him—he was the one who had taken the order for Harry's Firebolt to the post office, and now he had brought Sirius the passwords he needed to get into the Gryffindor common room.

He'd tried to break into the common room a few months ago, the night of Halloween—he'd made it all the way to the Fat Lady, but of course she had refused to let him inside without the password. In a fit of rage, frustrated at being denied after so long, Sirius had torn up her portrait and run off. It had been ridiculously stupid; he had accomplished nothing except to put the castle on higher alert. He'd been biding his time before trying to enter Hogwarts again—he suspected he wouldn't have many more chances to get Peter before he was found out.

Through Crookshanks and his own observations, he'd learned a bit more about Peter and the situation he was in: the Weasley boy he belonged to was named Ron, and he was friends with both Harry and the girl who owned Crookshanks. Peter had been living with the Weasleys ever since he'd framed Sirius for his death twelve years ago, passed on from one sibling to another. No one but Sirius and Crookshanks seemed to suspect he was anything but a long-lived garden rat.

And Sirius had learned about Harry, too—he was a third year now, and he looked so much like James it hurt Sirius's heart to see him. He was a Gryffindor, of course, and a Seeker on the House Quidditch team; Sirius had risked capture long enough to see Harry fly in Gryffindor's game against Hufflepuff. He was excellent, as good as James had been at his age…he would have caught the Snitch for sure if a bunch of Dementors hadn't swarmed the pitch and nearly gotten him killed. Sirius had been unbearably anxious after seeing Harry's fall, wondering if he was okay, until he'd spotted him laughing with his friends during his Care of Magical Creatures class a week later.

Since he'd snuck onto the Hogwarts grounds, there was one thing that had surprised him more than anything else: he'd expected to see Peter at Hogwarts, and he'd expected to see Harry, but he had never imagined he'd find Remus back at the school. Remus—his Remus—was now a Hogwarts professor, teaching Defense Against the Dark Arts. Sirius had seen him for the first time when he'd taken a class of sixth years out onto the grounds to practice dueling, and he'd nearly keeled over in shock at the sight of him. He looked older, of course, with graying hair and tired eyes, but he was smiling, calling out words of encouragement to his students and complimenting them on their technique. He looked happy, so much happier than Sirius had thought he would be without any of the Marauders to keep him company. It warmed his soul to see his Moony doing so well.

Once, on the night of November's full moon, Sirius had snuck beneath the Whomping Willow to try and meet Remus's wolf in the Shrieking Shack. If only he had a change to speak to Remus alone, he thought, while he was recovering from his transformation and too weak to fight, he could explain everything…but Remus had never come to the Shack, and judging from the layers of dust coating its floors and walls, no one had been there in years. Had Remus found another place to transform now that he was a professor instead of a student?

"Mrrow," Crookshanks said, interrupting Sirius's train of thought. Are we going to do this? he was asking.

Sirius flicked his ears in response—it was time to deal with Peter, once and for all. He began to dig through the earth at his feet until his paws touched the blade of the knife he had buried there—Crookshanks had smuggled it out of the kitchens a few nights ago. Taking the knife and the password parchment in his mouth, he followed Crookshanks carefully towards the front doors of the castle.

The cat sat down beside the doors and pawed at their wood, meowing until they drew open for him. The doors were used to admitting pets at all hours of the day who had wandered out onto the grounds—they had no reason to suspect that dog-Sirius was anything more than a lost pet coming in from the cold.

The castle was empty and eerily quiet this far into the night, illuminated only by the candles and occasional fires lining the walls. Sirius and Crookshanks made their way up to Gryffindor Tower for the second time, Sirius transforming back into his human self inside a little closet near the entrance to the common room. He had no wand, but he was able to summon a ball of fire to see by as he unrolled the paper Crookshanks had given him to find a long list of passwords organized by the time and day they went into effect. "Perfect, Crookshanks," he whispered. He had no idea who would have written down a week's worth of Gryffindor passwords, but this was just what he needed.

He stepped out of the closet with his fire, approaching the portrait guarding the common room. It was not the Fat Lady, he realized to his surprise, but instead a portrait of a knight astride a fat gray pony—Sir Cadogan.

"Who goes there?" Sir Cadogan demanded, drawing his sword menacingly at the sight of Sirius. James and Sirius had pranked the deranged knight countless times when they'd been at Hogwarts, sending him all over the castle on made-up quests, but Cadogan did not seem to recognize Sirius now. Sirius was hardly able to recognize himself in the flyers he'd seen posted of his face across the wizarding world, so it came as no great shock.

"Lancelot," he said, reading the night's password off of the paper.

"Right you are, good sir!" Cadogan said, and he swung forward to reveal the portrait hole behind him.

Taking a sharp breath, Sirius climbed through after Crookshanks, using his flame to examine the common room. No one was inside—Crookshanks had made sure not to fetch Sirius until everyone in the tower had gone to sleep—but the common room had clearly been the venue for a recent House party: there were sagging banners blanketing the walls and empty cans of butterbeer littering the floor. Sirius had been too preoccupied to pay much attention to the day's Quidditch match, but the evidence was certainly pointing towards a Gryffindor win against Ravenclaw. He grinned in spite of himself.

Crookshanks led him up the steps to the boys' dormitories, stopping beside one of the doors and meowing softly. Sirius extinguished his flame, teased open the door, and tiptoed inside.

By the moonlight streaming in through the dorm's back windows, Sirius could make out five four-poster beds occupied by soundly-sleeping boys. His heart squeezed at the sight of Harry in one of the beds nearest the door, twitching and mumbling in his sleep with his rounded glasses perched atop his nightstand. How he longed to wake him, to talk to him and tell him how much he looked like James….

But he forced his attention to the bed beside Harry's, where Ron Weasley slept open-mouthed with his curtains half-drawn. Sirius crept towards him, slashing through the curtains with his knife and looking for a rodent nestled among the bedsheets. But he found nothing—Crookshanks climbed over Ron's legs and sniffed around, but he came up just as empty.

Peter wasn't here. He must have figured out that Sirius was after him, and he'd fled. Shit. Shit, shit, shit.

Suddenly Ron's body gave a lurch, and he lifted his head off his pillow, blinking open his eyes with a yawn. Sirius froze, the knife trembling in his grasp.

Ron's eyes went first to Crookshanks, then to the armed man hovering over him. There was one final moment of silence, the boy's eyebrows shooting up into his hair and his mouth gaping open….

"AAARRGGHH!" Ron screamed, shrill and loud and terrified. "NOOO!"

Cursing under his breath, Sirius wheeled around and sprinted from the room with Crookshanks at his heels just as someone flicked on a lamp behind him. He ran and ran, changing from dog to human and back again until he was out of the castle, returning to the safety of the Forbidden Forest while anger and frustration rolled off of him in waves.

Peter was gone, possibly for good, and Sirius had failed for the second time. Now what am I supposed to do? he wondered as crouched among the trees and Crookshanks circled around him with his haunches bristling.

But the cat didn't have an answer, and neither did he.