That day, Professor Snape took a strange turn. Instead of his usual snide comments Harry had expected him to furbish them all with, he was at first silent and then, to everyone's shock, remotely friendly. True, he did try and detract over seventy marks from Gryffindor before he realised they weren't actually at Hogwarts, but at least he didn't shout at them unless he was provoked. Harry wondered what could have happened to him. He seriously doubted that it could be remorse: suspiciously, Harry wondered if it wasn't some kind of trap. He said as much to Ron, who nodded wisely.

"I can't think what else it could be," he agreed, as he watched Snape say something to Lupin without the familiar loathing they'd grown accustomed to the year before last. It was extremely puzzling. There was still a deep resentment there – certainly dislike – but not the bone-deep hatred there had been. Ron shook his head.

"Mental," he said. "He's gone mental. I bet he's just waiting 'til we get to Hogwarts and then he'll turn back into his usual charming self."

They had stopped for a while, in a small clearing in the forest, which, it seemed, stretched on forever. From what he could gather from Sirius, there appeared to be a direct route from it to the woods at Hogwarts… Harry shook his head. He had long since given up trying to work out what was happening. But at least there had been no sign from the howling thing – whatever it had been – and his scar hadn't hurt again since that night.

He, Ron and Hermione were sitting to the right of Snape and Sirius – Lupin had disappeared, he said to check on their route. It was a relief to sit down: Harry had never ached as much as he did now, not even after his most disastrous games of Quidditch. And there had been a few of those. Hermione had sunk deep into the muddy soil, and lay there muttering to herself. Ron stared at her, perplexed.

"Who are you talking to?" he asked curiously.

Hermione blushed. "No one," she said, looking far more flushed in the face than usual. Harry decided she was ill.

"Oh," said Ron. "I thought you were talking to yourself."

"Well – why would I do that?"

"Because you're the only person that would ever listen…"

It hadn't been funny, but after Ron had spoken a strange, high-pitched snickering noise came from their left, and Harry felt his friend clutch at his forearm painfully.

"Harry," he said quietly, in an odd, wavery sort of way.

"…Yes?" asked Harry, anxiously.

"Was that my imagination, or… or did I… was it…"

"No, no," Harry assured him, removing his arm from his friend's grip. "That was Snape laughing."

Ron looked like he might faint any minute, and Harry pushed him gently down onto the ground.

"There, there," he said, unsure of how to comfort his friend. "I'm sure it wasn't anything personal…"

They carried on walking again, Ron still slightly nervous and avoiding eye contact with Snape, who seemed either oblivious to the fact or perfectly happy with it. Ron, as well as Harry and Hermione, was still having difficulties in accepting Snape's new character.

"Maybe it isn't him at all," suggested Ron, after a while. "Maybe its someone drinking Polyjuice. Maybe he's like Barty Couch last year – y'know, when he was pretending to be Mad-Eye Moody, and everything."

"Maybe someone's put a spell on him," said Hermione.

"Maybe Lupin damaged something permanently when he knocked him out," said Harry hopefully.

"I don't think so," said Hermione, doubtfully. "He certainly looked like he wanted to kill Sirius back at the house."

"Ah," said Ron darkly. "But that could have just been an act."

"Question is," said Harry, "Who would ever want to pretend to be Snape?"

They pondered the question for a while longer, before they realised that doing so had made them drag behind and the others were waiting for them a good twenty yards or so ahead. They hurried to catch up.

"Professor Lupin," said Hermione, sidling up to him, "What have you done to Snape?"

Lupin looked at her in surprise. "Nothing," he answered. "What makes you ask?"

"He's – he's being nice to Harry," replied Hermione, backed up with vigorous nodding from Ron.

"And he's talking to Sirius," he added. "And he laughed. He laughed, at my joke."

"Why shouldn't he?" enquired Lupin, apparently amused.

Ron shrugged, exasperated. "You know what he's like," he said. "We all do."

Lupin looked at him thoughtfully. "Do we?" he asked pointedly. "We all see the side of Snape he lets us see – but everyone has more than one side to them – I should know."

Hermione and Ron fell silent at this, and Lupin continued. "Snape may well be whatever you want to call him most of the time," he said, "He may be a fool when it comes to holding grudges against the wrong people. And yes, I have absolutely no regrets whatsoever about knocking him out the other night. However," he said, holding up a hand to stop Ron and Hermione from laughing – the image of Snape getting knocked unconscious was still too much for Ron especially to take – "However, he is a brave man, I don't deny it. He has done what few supporters of Voldemort would ever have dared to do. And he is on our side. Dumbledore trusts – even likes him, I think, and I for one am content to lean on his judgement. Watch where you're going, Ron," he added, snaking out a hand and just preventing Ron in time from making the same mistake Harry had made earlier. A loop of rope was lying in the middle of the path, and Ron had just been about to step into it. He spent the next half hour staring fixedly at the ground.

Apart from breaks to catch their breath, and for lunch, they didn't stop until just before nightfall the next day, when the dusk had settled into something a little darker. It was cold, and Harry wished not for the first time that they were in the main hall at Hogwarts, surrounded by warmth and tucking into one of the school's famous feasts; there would be chicken legs marinated in ginger and celery, swiss rolls with huckleberry jam, chocolate and aubergine flavoured steamed puddings…

"Harry?" Startled, Harry look round into Hermione's worried looking face.

"What?" he replied.

"You fell asleep. Look, Sirius and Ron made a fire over there – Ron had better luck with matches than his dad…"

Harry couldn't help but laugh as he remembered the time Mr Weasley had excitedly gone through seven boxes of matches in an attempt to light a 'Muggle' fire at the Quidditch World Cup last summer. Ron's dad had loved every minute of it, but Harry was glad that he didn't usually have access to that particular means of lighting fire – and also, as he watched Ron blow encouragingly at the flames, that his inaptitude with them wasn't hereditary. He walked towards his friend with Hermione, and huddled up in his robes.

"Who's going to cook dinner, then?" asked Ron, staring rather pointedly at Hermione. She took offence at this.

"Typical male attitude!" she exclaimed shrilly, startling both Lupin and Sirius, who were sitting beside her. "That is so typical! Hermione is female – Hermione can cook – Hermione can – "

Ron muttered something very quietly under his breath. It wasn't, unfortunately, quiet enough, though: Hermione had heard. She turned pink with anger.

"Ron can cook supper," said Professor Lupin swiftly, before Hermione could deliver her stinging retort, "With me. OK with you, Ron?"

The prospect of cooking supper was apparently infinitely more agreeable to Ron than hearing whatever it was Hermione had been about to say, and he nodded vigorously.

"Yes," he said quickly. "Yes, yes – fine – I was just about to offer…"

Hermione grinned triumphantly at Harry, and he gazed back, shocked. This had obviously been well planned out.

So, while Ron and Lupin tried to cook the food they had taken with them from Sirius's house, Harry and Hermione sat by the fire and dozed. Sirius and Snape had disappeared (in opposite directions), and Harry listened vaguely to Lupin telling Ron something about one of the Hufflepuffs turning a Boggart into a joint of ham with eyes last year when he had taken a Defence Against Dark Arts lesson, that materialised into a spider when she had shouted "riddikulus" at it – at which point Ron hurriedly backed away from whatever it was they were cooking – and then he drifted off into a shallow, fitful sleep.

He was woken what seemed like minutes later by a nervous looking Ron standing above him prodding him with his toe.

"What d'you want?" Harry mumbled sleepily at him.

"Um – Lupin wants me to go and give Snape this?" whispered Ron, holding a cup of tea in a shaking hand, his voice rising oddly at the end of his sentence.

"Well, fine," said Harry, wondering what this had to do with him and why Ron had bothered to wake him up to tell him.

"Want to come with me?" continued his friend, with a forced brightness. "It'll be… it'll be fun…"

Harry stared at him like he'd gone mad. "Fun," he repeated blankly. Ron scowled.

"Well OK, it won't be, but – are you coming or not?" he snapped.

"Why do you need me? Snape isn't going to bite your head off, Ron," Harry replied sleepily. Ron didn't look quite so sure.

"You're just scared of him," he announced as Harry rolled over to go back to sleep. "Fine then. I'll go by myself. But if – if I don't come back…" His voice shook a little. "If I don't come back – well, don't expect me to leave you anything in my will, that's all!"

He stormed off.

By the time Ron had located Snape, the tea had gone cold and he was beginning to wonder if he was lost. But he found him at last, sat next to another small fire in the shelter of a hill, long nose buried deep in a book.

"Er – professor?" tried Ron, tentatively.

"What do you want?" said Snape ungraciously, then seemed to reconsider. "Er – what… what is it?" he asked, slightly less savagely.

Ron stared at him, curious. The first question, he'd been expecting: the second – or rather the tone of voice of the second – threw him totally.

"I – um – Professor Lupin made some tea," he said finally. He put it down on the ground in front of the Potions master. "Here you go."

Snape appeared to make a conscious effort to seem grateful. "Thank – thank you, er… Ron," he managed at last, choking the last word out.

Ron stared for a minute longer, then backed away, slowly. Perhaps Snape was ill.