Marauders on the train

A/N: Note that this fic is based on the scene from the film, not the novel.

Remus was play-fighting with his closest friends in the Shrieking Shack. This was the first time his friends had successfully accompanied him down past the Whomping Willow, and he marveled at the warm feeling of affection he had for these three, the ones that had risked so much in this display of solidarity. It even threatened to banish the irresistible drive to hunt, to kill…..

Sirius gave a nip at his furry hindquarters, and Remus turned to snarl at the audacity of his rebellious friend. It was winter and night had fallen, but with such a layer of fur, and in his manic, transformed state, he hardly felt the cold.

But that began to change. He heard the creak of a door in the distance, a sudden, muffled roar of what he assumed to be wind, and cold like he had never felt before rushed over him. He heard, yet again, the sounds of Fenrir Greyback opening the door to his bedroom when he was five, knowing the unimaginable pain that was soon to surely follow.

Another roar of wind…

Remus John Lupin opened his eyes. He knew he was on the Hogwarts Express. But what had awoken him? He already half-knew the answer, and his fear was confirmed as he sat up to take in his surroundings.

As the Dementor inhaled with that ghastly sound that its kind made as it moved further into the compartment, its hands extending towards a passenger, Remus quickly looked at the creature's chosen victim – a young teenager with familiar jet-black, messy hair – and he acted.

Doing his utmost to recapture the happy dream that was still clear in his mind, he drew his wand on the attacker. The energy waves of his non-corporeal Patronus hit the Dementor full on, distorting and rippling its hood as it backed out the door. However, Remus felt another wave of cold as the Dementor sucked helplessly at the Patronus, remembering the utter helplessness he felt as he was told that Peter too had been killed and that his remaining best friend had been arrested for the murder of thirteen people. He heard a thump from beside him, but kept his attention focused on the Dementor as it was driven out of the compartment and down the corridor.

Stowing his wand, Remus looked down at the fallen form of the boy he had protected, spread-eagled across his seat and staring blankly at the ceiling. With a jump, Remus stared into Lily Potter's eyes for the first time in nearly twelve years. As he stared, Harry feebly stirred, closing his eyelids. It was only now that Remus noticed the tell-tale mark left by Voldemort's curse.

The movement of both the other human occupants of the carriage snapped Remus out of it. He cleared his throat, moved to the corridor outside the carriage, and looking back nervously to ensure Harry's friends weren't looking, sent his Patronus to the driver. This time, his silver wolf darted away from his wand.

He nodded in satisfaction as the lights re-ignited and the train slowly began to inch forward, the movement cracking and shattering the accumulated ice on the windows. Returning to the compartment, Remus saw that the bushy-haired girl and the redheaded boy were exchanging worried glances and noticed the girl was clutching the boy's elbow as she started at their unconscious friend. They must have been Hermione Granger and Ronald Weasley, Remus realized, remembering that Dumbledore had already told him about Harry's two tumultuous years at Hogwarts with his two friends. As Harry stirred, they both abruptly moved away from each other and kneeled beside their friend. Remus moved in too, eager to assist.

As Hermione moved in to hand Harry his glasses, Remus produced a chunk of Honeydukes chocolate, noticing as he did so Ron and Hermione's pets: a distinctly moth-eaten rat, and a ginger cat with a squashed face. Something about the rat puzzled Remus. Harry's query put it out of his mind.

"What – what was that thing?" Harry finally managed, accepting Remus' chocolate. "That came?" he added, staring fearfully back towards the now thawed corridor.

"It was a Dementor," Remus replied with distaste. "One of the guards of Azkaban. It's gone now, it was searching the train for Sirius Black." His anger at the Ministry for such a heavy – and flawed – security arrangement was rapidly redirected towards his former friend. If he hadn't given in to Voldemort, none of this would have been necessary.

Then the old doubt in his mind resurfaced. Sirius had never been the type to retreat in fear, no matter the danger of whatever Order operation he was assigned to…

But there were more pressing engagements than psychoanalysing Sirius, or whatever he'd become. Like, for instance, informing the driver of how a student had nearly been Kissed by the very thing stationed to protect that very same student. He placed the rest of the chocolate bar beside Harry as he stood up.

"If you'll excuse me, I need to have a little word with the driver." He looked back at Harry one last time from the doorway and noticed his pallid complexion. What horror had affected him so badly? Surely he couldn't recall any part of that Halloween night? There was only one remedy for that, he knew.

"Eat!" he said sharply. You'll feel better." And with that, he left Harry, Ron and Hermione to their own devices.

As he approached the divider between carriages, Remus halted with a sigh. Although a valid course of action, having a word with the train driver also served as a convenient excuse to calm himself from the shock of seeing Harry for the first time in over a decade. He would have to do better as a Professor, he reasoned.

He was positive that he hadn't revealed his lycanthropy – but what if someone spotted the tell-tale scars crossing his cheeks and put two and two together with the Patronus?

That wasn't the only thing bothering him though. He knew one fact about Sirius that no-one else alive did. And the result was that Dementors were completely ineffective. The only responsible thing to do was to tell Dumbledore as soon as he arrived. Remus' cowardice in not informing the Ministry or Dumbedore had already had a consequence. Protecting Harry was key, and if only he'd told someone – anyone – about Sirius' status as an illegal Animagus, the Dementors would never have been called in, and Harry would never have been attacked. Not for the first time, he cursed his former friend's ability to harm Harry without cursing him or even touching a hair on his head.

He shook his head. That was too simple. Sirius had escaped Azkaban. No dog could ever survive paddling that distance to the mainland in hurricane-force winds, a high swell and poor visibility. He must have used dark magic learned from Voldemort.

As Remus struggled with his guilt, the thought of why Ron's rat had bothered him never again entered his head…

Unknown to Remus, another Marauder was present on the train. And this Marauder was trembling in Ron's hands. Being a rat did not fully insulate him from the Dementor's effects, unfortunately, as this individual recalled the time of his meeting with Voldemort as well as the sharp pangs of regret that came with it. He'd given into his fears, and there was now no going back.

Remus had then seen him up close, and even with the loss of fur and his toe, for one moment he'd been absolutely certain his old friend had recognized him. The only positive aspect of the Dementor's entry into the compartment had been that cat ignoring him. Speaking of the devil….

Crookshanks looked up from his owner's lap, stared at him with a piercing, knowing gaze, and hissed.

At that, Peter Pettigrew dived into Ron's jacket pocket, where he remained for the rest of the train journey.