Disclaimer: I do not own Harry Potter, JK Rowling does.
The Wizarding World was truly and simply an uncanning, mysterious, beautiful and terrible place. It was backward, compared to muggle civilization, yet it was forward in other aspects. Muggle roads would be filled with smoke from all sorts of vehicles, whereas all wizarding cities were free from pollution. Even the Hogwarts Express which was created by a muggleborn was powered by only a simple steam engine. Train accidents happened in many muggle cities on a daily basis, in undeveloped as well as developing countries, while the Hogwarts Express was yet to report an accident, as its muggleborn creator knew that if there was a single accident or a single casualty, muggleborns wouldn't be able to show their face anymore. In spite of many threats to stop, the Hogwarts Express Project was a huge success. All security measures inside it were state-of the-art. In fact, there were children who hid in the Hogwarts Express in the last war, and escaped unscathed.
The Hogwarts Board of Governors consisted of one muggleborn, six purebloods and three half-bloods. The six purebloods made sure the Hogwarts Express was never mentioned as a muggleborn creation n in Hogwarts, A History.
The total human population of the Earth was approximately seven billion. The magical population of the Earth was only seven million. The population of magical Britain was only one million, inclusive of squibs. Wizards used to be terribly afraid of muggles before the development of the Statute of Secrecy and Muggle-repelling charms. But in the later years, that fear had transformed to hate.
Harry had thought of leaving the Wizarding world once. He could easily get a job in the muggle world. After becoming of age, a Confundus charm on an unsuspecting muggle would do the trick. But even the poorest of wizards would never do that for money.
Harry's thoughts were interrupted by Hermione and Ron. Hermione told him about wanting to form a defense group. Harry said, "Hermione, if we get caught, we'll be expelled for sure. I've just had a narrow escape from the ministry. I can't go through another ordeal". But Hermione was persistent. While Harry understood the merit of her idea, he didn't have the support of all the students. Besides, Harry wanted to spend his free time in his personal interests. He offered Hermione something else though. He took her to the seventh floor and showed her the Room of Requirement.
"You can practice magic in here, without interference", said Harry. Hermione was amazed. "All you have to do is walk past this portrait three times, thinking clearly of what sort of place you want. But beware, the room can be entered by outsiders if they know how the room is being used. So make sure to tell the room to bar anyone outside your group from entering". Harry had found out all of this by experimenting with Dobby's help.
Inside the Chamber, Harry shouted Serpensortia. A harmless garden snake appeared. Just as he was about to hiss a command, the snake disappeared. This was the progress he had achieved, after one hour of practice for six days. More than an hour each day would lead to magical exhaustion. The conjured snake lasted for only three seconds. He decided to practice everyday. After that, Dobby popped him to the restroom and disappeared. This was to avoid detection.
That day, when Potions was over, Snape told him to stay behind and dropped a bombshell on him. Snape was going to read his mind and discover his ideas and secrets. Harry was thoroughly distressed by this new unexpected development. He didn't know how to escape this. After an whole hour of tremendous thinking, he turned to the portrait of Master Smith kept in his trunk. He told him about this problem. Smith gave him a single solution.
"Use your house-elf. House-elves can synchronise their magic to protect their master's mind for a short period of time.. But, the elf has to be near you during the Occlumency lessons. Tell him to accompany you during the lessons, while remaining invisible. But if your mind appears completely blank, Snape might suspect something. Select the list of memories which you want to be hidden and tell the elf to hide those memories alone. That way, it wouldn't drain his magic very much, and he might be able to protect your mind a little bit longer".
Harry thanked him for his advice and went straight to Dobby. Harry showed Dobby all those memories which needed to be hidden so that Dobby would know what to do at the right time."
The cleaning of the Chamber was still ongoing. Dobby was doing excellently. Master Smith, through his portrait was teaching Harry a difficult Charm, which would pull out the entire skeletal structure of the basilisk away from the body, without making even a small cut on the body. It was a modified version of Brackium Emmendo (cast by Lockhart earlier). Instead of healing the skeleton, it would relocate it. Harry wished Dobby could do this by simply snapping his fingers. Unfortunately, it seemed that Dobby could not do several things which wizards could, which had surprised him tremendously. It must have been due to the lack of a wand, he thought. Harry was practicing this spell on a rat which Dobby caught. Smith refused to divulge the purpose of learning the spell until after he had learnt spell would take atleast two months to learn.
Back in the Common Room, Sirius appeared in the fire. "Harry, I want to accompany you during the Hogsmeade weekend as Snuffles". Harry said, "Sirius , I have Polyjuice with me. I brewed it earlier. I shall mail it to you. Use a muggle hair or something and come along. It'll be better that way". Sirius beamed. Hermione was disapproving of this, but he didn't care. So it was decided. Harry enjoyed the weekend with Ron, Hermione, Neville, Sirius and Luna. After that, it was time for another plan to be put into motion.
Harry added a muggle hair into his Polyjuice Potion, drank it and waited for Mundungus to arrive in the Shrieking Shack. It was a reckless plan, not to mention highly illegal. But if anyone could do it, it was Mundungus. And so, he had written a letter to Mundungus, using a school owl. It would have been highly suspicious to use his Hedwig as McGonagall and Hermione had once warned him. The letter had the following content:
I have a job for you, Mundungus. Meet me where Moony used to transform in Hogwarts. If you complete the job successfully, I shall reward you fifty galleons. Come alone, otherwise you will lose your reward. Do not speak of this to anyone.
The letter had been left unsigned. Just as Harry expected, Mundungus arrived.
"Who are you?"
"That is irrelevant" And he told him he job. Mundungus wasn't alarmed, which surprised Harry greatly, and also made him even more wary of Mundungus. Mundungus readily agreed to the job, without batting an eyelid. Harry provided him Polyjuice Potion. The deal was sealed.