It was a Friday evening at the beginning of Harry Potter’s sixth year at Hogwarts School of Witchcraft and Wizardry. Severus Snape, the Potions Professor, put another parchment on top of the pile of corrected tests, thinking about the boy it belonged to: Harry Potter. During the recent summer holidays, it had become necessary to retrieve the boy from his relatives and keep him safe at the castle. At first, Severus had been terrified when Dumbledore forced him to take the guardianship over the boy. However, during the time that teacher and student had been living together in his quarters for two months, they had gotten to know each other and had learned to get along well.

Suddenly, a knock on the door of his office pulled Severus out of his thoughts. It was Draco, his godson.

“Uncle Severus, I need your help,” Draco said, letting himself fall onto a chair next to Severus’ desk. When Severus gave him an enquiring look, he continued, “You know about the order I received from the Dark Lord, Uncle Sev., don’t you?”

“Yes, Draco. He told you to give him detailed information about the underground rail network in London, right?”

“Yes, and I just went there after my afternoon lessons, but I couldn’t get in. I’ve no idea how to get through the barrier, and I couldn’t ask anyone as the place was flooded with Muggles who seemed to know exactly what they had to do.”

“All right,” Severus said pensively. It couldn’t be so difficult to get behind a simple Muggle barrier now, could it? Even if it was necessary to obliviate a few Muggles. He glanced at the clock on the mantelpiece. “Today it’s already a bit late, Draco, but we can go to London tomorrow morning. Come here to my office straight after breakfast.”

Draco gave him a relieved nod. “Thanks, Uncle Sev.”

-----

Directly after breakfast, Severus and Draco took the Floo to The Leaky Cauldron, entered Muggle London, and walked over to where Draco had seen the Tube station the day before.

Severus looked around flabbergasted. That was nearly worse than Kings Cross. And he had no idea how to cross the barrier either. They couldn’t obliviate hundreds of people.

“Maybe we have to buy a ticket at one of these machines,” he said pensively.

They walked over to one of the machines, looking at it closely. The machines obviously sold tickets but the two wizards didn’t have a clue which ticket to buy and how to operate the machine. After an hour of studying several plans and trying out the machine, Severus shook his head. “No, Draco, that doesn’t work. We have to bring Harry with us.”

“Potter?” Draco shouted terrified. “Why?”

Severus raised an eyebrow. “Harry grew up with Muggles, so maybe he knows such things.”

The two wizards quickly returned to Hogwarts just in time for lunch. Severus immediately cornered Harry in the Great Hall and asked him to help them, telling him the problem.

“Why would I help Malfoy?” Harry asked stubbornly.

“Perhaps because he is my godson and you can imagine what the Dark Lord would do to him if he failed? Or perhaps because people helped you when you needed help?” Severus returned, raising an eyebrow.

“Oh, yes, all right,” Harry replied immediately, thinking about how Severus had helped him after rescuing him when he was injured in summer. “I’m sorry,” he added in a soft tone.

-----

After lunch, Severus, Draco, and Harry went once more to London to research the workings of the Tube. At the beginning of the summer holidays, Harry had used the Tube once in order to visit Dean Thomas. Therefore, he knew how to buy a ticket and to get through the barrier. However, he didn’t have a clue in which direction they had to head after passing the barrier. They walked around indecisively for fifteen minutes before they decided that it didn’t really matter which train they took as they’d come back and get off the Tube system at exactly the same station where they were now.

The three wizards took the first Tube that arrived, heading in an unknown direction. Another ten minutes later, they got off at a random station examining the platform. Suddenly, Harry had an idea.

“Will you be taking Voldemort here, Malfoy, or are you just going to explain to him how it works?”

“I suppose he wants to see it for himself in order to plan whatever he intends,” Severus answered darkly. “If you have an idea how to prevent that, then be my guest.”

“Yes, I have an idea, a very good one if you ask me.” Harry quickly explained to his guardian and his classmate a few things about electricity that he remembered learning at the Muggle primary school. Seeing that the two wizards were looking at him in awe, he let them in on his plan.

“That doesn’t sound too bad,” Severus replied pensively.

“That’s just brilliant,” Draco shouted excitedly. “Uncle Sev., can you accompany me when I have to take him here?”

Severus sighed. “You have to ask the Dark Lord if he would mind me accompanying you. If he doesn’t object, of course, I shall come with you. Unfortunately, we cannot take Harry with us.”

Harry snorted. “No, sir, that wouldn’t be a very good idea."

-----

The three conspirators didn’t have to wait long. On Sunday morning, Draco was called to Voldemort. He explained a little about what they had found out about the Tube and told the Dark Lord that he would like to take him there in order to show him several things and explain something very interesting about Harry Potter. His Master agreed, and when Draco asked if Severus could accompany him as he wasn’t too sure how to buy tickets and find their way, Voldemort called Severus with the Dark Mark. Ten minutes later, the three wizards were on their way to London.

---

Voldemort in his total rejection of everything Muggle looked at the Tube and thought, ‘How primitive these animals are with their means of transportation!’ Unfortunately for him, he was blatantly unaware of some of the more fundamental principles of Muggle sciences, in particular the principle of electricity that Harry had explained to Severus and Draco the day before.

Severus and Draco looked at one another, thinking of the plan they had hatched together with Harry. It was now or never. “Master,” Draco suddenly shouted. “Potter uses these strange metal rails to enhance his magic, and we’re not able to find out how it works.”

Jumping down onto the rails, Voldemort inadvertently touched both the main rail, and the live rail which conducts the electricity. In a blinding flash Voldemort opened his eyes and realized all was not well.

With a twinge, Draco and Severus noticed that their Dark Mark was fading into non-existence, while at Hogwarts, Harry’s scar burst with pain and emotion before everything returned to normal apart from the fact that Harry’s scar was now gone.

Maybe, Voldemort had just learned a very vital lesson. When the teacher is telling you something in Muggle primary school perhaps you should listen – you might learn something very important. And Harry Potter had just discovered the power he knew not – the magical properties of electrical power.