From Azkaban to Hogwarts.

The first day of the Easter holiday was sunny with a gentle breeze.

Inside the room at No. 6 Privet Road, Lu Ping, dressed in his robe, lay on the sofa, playing games absentmindedly, feeling that something was amiss.

Sirius was called down to the basement to work on the potion. He wanted to go and help, but William and Mr. Belby shooed him out with looks of disgust—yes, he was sure they were looking at him with disgust.

Moreover, there is factual evidence: after he was expelled from the underground laboratory, William took out a bottle of potion in front of him and, together with Mr. Belby, used a wand to clean up the laboratory with the potion…

If it weren't for the occasional snacks he would receive from William, his somewhat insecure and fragile heart would have almost thought he was being ostracized—of course, Lupin himself would never admit that he was fragile.

"What are they doing, researching potions? When did that Bigfoot guy ever get good at potions?"

He thought to himself with a hint of anger.

He acknowledged that, after the Animagus transfiguration, the Bigfoots were far ahead in transfiguration.

He also admitted that Bigfoot was the one who shone brightly in what was then known as Defense Against the Dark Arts class.

But as for potions—it's safe to say the two of them wouldn't actually brew poison.

'Leave me here alone…'

He thought to himself irritably, but still felt that something was wrong—but he didn't have time to think about it now, what exactly was Bigfoot studying?

-

"Very good, the blood, hair, sweat, and saliva have all been collected!"

Belby nodded at Sirius, a genuine smile on his face—sampling was easy for ordinary wizards, but this one was different. There were only seven Animagus registered in the 20th century, and even if you include the one in front of you and Rita Skeeter who was still in Azkaban, there were only nine. And now it's almost the end of the century!

Even if he were a top potion master who researched wolfsbane potions, it wouldn't be very feasible to get all these people to cooperate in sending samples, since there were simply too few Animagus.

"Please, Mr. Black, please cast the Animagus transformation spell once. We still need to collect some materials after the Animagus has transformed!"

He looked at Sirius with a sincere expression, hoping that he would cooperate as always.

Sirius, looking utterly helpless, was simply too exhausted to speak—he had come excitedly to help improve the potion, but little did he expect that the research wouldn't be on the potion, but rather on himself…

But he also said that he would fully cooperate with this matter, and that the results would be directly related to Lu Ping, which made it impossible for him to refuse.

With a touch of despair, he completed his Animagus transformation unhappily for the first time in his life.

"good, very good!"

Mr. Bellby stared wide-eyed at Sirius with a look of surprise, then pulled out a knife and a variety of glass bottles.

Sirius was so frightened by the way they were about to take him apart that he instinctively looked to William for help, only to find that William was already washing and drying the container with a stream of clean water.

"First the hair, then the hair on the torso, and then some saliva and blood."

Mr. Bellby skillfully completed a series of sampling activities, then looked at Sirius with anticipation, "Please, Mr. Black, can you run around a bit? We need to work up a sweat!"

“Mr. Bellby…”

William suddenly stopped him, which made Sirius feel relieved.

Then, William's rather emotionless voice rang out, "A dog's sweat glands are on its tongue, and there are also some on the soles of its paws, both of which are easily contaminated..."

???

"It's okay, mixing them together might create an even more amazing effect!"

Although he had a bad feeling about it, Sirius still hesitated and completed all the tests.

"Alright, that's all for now..."

William, beaming with delight, said to Sirius, "Let's go back to our original forms, Mr. Black..."

He and Belby sorted and packaged the collected samples, and in front of Sirius, they took out the previous potions again and began cleaning the entire laboratory environment.

"Please, could you please call Professor Lupin in?"

"Of course, I couldn't be happier!"

Since there was no risk involved, Sirius decided to become the biggest risk to his brother, and happily ran out, then called Lupin in.

When he saw the joy on Lupin's face as he saw William and the others being disinfected, he hummed a little tune, lay down on the living room sofa, and took over the handle that Lupin hadn't really warmed up.

"I feel like I've forgotten something—but it doesn't matter, Moonface would never have imagined his good colleague would be so ruthless to him..."

-

"Sampling is now complete..."

William finished his work again and spoke to Mr. Belby in a muffled voice over his bubbly head.

"Actually, it's still a little short, but considering the users' feelings, let's just forget about it..."

Mr. Belby shook his head, opened the container of Lupin's hair, and took out some to give to William and himself. "I've been studying werewolves for many years. Because of that special curse, there is actually a faint, non-contagious curse in their hair."

"Is that so?"

William looked up at Mr. Belby; he had never heard of or seen such an idea before.

"Yes, but I think it's my own unique discovery—after all, there aren't many wizards willing to study werewolves."

He spread his hands, the dragon-skin gloves reflecting a beautiful light. "But I secretly kept this discovery a secret—they already suffer enough discrimination. It would have been much worse if it weren't for some preferential treatment laws passed before Umbridge's identity was exposed."

"Yes, that was one of the few bright spots in her life of many evil deeds."

William nodded. "Shall we use potions to extract those curse attributes as testing agents?"

“Of course, that works very well—if possible, please do it your way, Professor William. I’ve been wanting to see it for a long time.”

"Extremely happy to."

William smiled and began processing the materials using his unique methods—this was the kind of exchange he had always dreamed of between pharmacists. How could someone like Adams, with his biased view that not knowing Felix Felicis meant he couldn't be a pharmacist, possibly have a proper conversation?

Hogwarts does have genuine potion masters, but such an exchange is unimaginable—Adams could just laugh it off and still get his hands on high-quality herbs, while William simply couldn't be sure if the potion master at Hogwarts intended to poison him…

After carefully preparing the extracted potion, William immersed Lupin's hair into the potion and then began to observe Mr. Belby's potion-making process—a perfectly normal part of any exchange activity, as one would be ridiculed by their peers if they couldn't guess the method.

'A more sophisticated formula, significantly more expensive, but the effects are undeniable. It's more than 10% more precise than mine, which is a remarkable change…'

As William observed and learned, he subconsciously began to speculate.

Wow, what a great combination!

Bellby echoed the sentiment, "The cost has been reduced by more than half, but the performance has hardly changed!"

The two exchanged a few compliments before realizing it was unnecessary. They then proceeded to mass-produce Lupin's hair—Professor Lupin, who was usually very well-groomed, was now shaved bald. Such a huge sacrifice was not to be wasted.

Their next experiment required the use of a large number of reaction agents, trying out various potions combined with materials obtained from Sirius to suppress the curse. Although they had the Wolfsbane potion as a base, it was still a huge undertaking.

“Oh right,” William said, having finished grooming his half of the hair, when he suddenly remembered something, “I almost forgot to remind them, I have to go out for a bit!”

He opened the laboratory door, strode into the living room, and coughed softly towards the two Gryffindor graduates who were mocking each other in the distance, so as to preserve their dignity.

"Ah, Professor William!"

Sirius Black stood up with a serious expression, his hair missing a lock. "Is there anything else you need?"

He couldn't be happier at this moment—Lupin had been almost completely shaved, and Lupin was trying to grow his hair back with his wand, but Lupin kept stopping him, determined to laugh at him to the end.

Everyone else was treated as research subjects, and you were the one who got your head shaved!

Hahahaha!

"I almost forgot something important, Professor Lupin, did you use magic to help your hair grow?"

"I just made a tiny bit..."

“Ah…” William slapped his head on his hair-bubbling spell. “Shave all your hair off and let it grow naturally. Magically induced hair growth can easily affect the experimental results.”

???

Lupin almost wondered if he had offended the office director, but seeing that William's expression didn't seem to be joking, he could only reluctantly promise to do as he was told.

"Hahaha…"

Sirius was laughing very happily.

“Oh, and you, Mr. Black,” William turned to Sirius, “you haven’t used magic yet, have you?”

"No."

Sirius smiled and said, "A new hairstyle can cover it up; it's not a big problem."

“That’s great.” William nodded. “We need to conduct an activity comparison experiment, so we will be collecting hair samples in succession. Please be sure not to apply any magic to the hair.”

"Use?"

Sirius's voice trembled slightly.

"Yes, we'll use some of it for comparison. We'll keep some for use and use some on the same day. We'll do this every day, so please don't use any hair care products with magical properties recently, and please don't use magic to make your hair grow. Please."

"That's all for now. I need to go back and deal with the medicine."

After giving instructions to the two men, William returned to the outer layer of the laboratory, disinfected himself again, and then entered the experimental area to resume the experiment.

"Ha ha ha ha…"

The usually stern Lupin looked at his good friend Bigfoot and couldn't suppress his heartfelt joy. Although he felt a little guilty about his friend's sacrifices, well—sorry, Bigfoot, taking so much from him is just too much…

"Hahahahaha..."

Laugh, laugh…

Sirius glared at Lupin, leaned back on the sofa, and turned to look in the mirror—his reflection showed a full head of hair, but who knew what it would look like in the days to come…

"That's right!"

He suddenly remembered something, looked at Lu Ping, and there was a hint of panic in his eyes.

"Harry is still at the Weasleys' house!"

"Oh my god, we forgot!"

Lupin finally realized something was wrong—Harry wasn't there!

The two were a little anxious, but then they looked in the mirror.

"Wait, Bigfoot..."

Lupin's sense of responsibility as the Wanderer's brain, accumulated over the years, surfaced: "Are we really fit to show Harry what he looks like now?"

One is a godfather, the other a professor; if Harry saw their hair, it would really…

"But we always have to go out!"