“Your mother was quite the talented Potions Witch, Harry. She could brew anything from Wolfsbane to meth. It was truly a sight to behold”
“WHAT?!”
“Well, how did you think they kept me in check during the full moon?” Lupin replied calmly. “The Potions professor in our era was nowhere near as good as Snape is today, so I had to get my Wolfsbane from somewhere.”
“NO, I MEAN THE METH THING!” Harry shouted. “WHAT DO YOU MEAN MY MOTHER COOKED METH?!”
“Well, she didn't at first. But the Order was running out of money during the war, and we needed a way to convince the residents of Knockturn Alley not to side with Voldemort. Your mother provided a solution.”
Lupin nodded thoughtfully.
“She introduced us to a wonderful Muggle substance called meth. We had Mundungus deal it in Knockturn Alley. It made us enough money to last through the war, and the residents agreed not to side with Voldemort as long as we kept supplying them.”
“I—WHAT—WAIT—MY MOTHER WAS—HOW DID SHE EVEN—WHAT?!”
“Oh, don't worry, Harry. She stopped cooking after she became pregnant with you. For your health, she said.” Lupin tried to placate him.
Harry stared at him, utterly speechless.
“...Of course, it turned out that Voldemort had been buying from her supply. When she stopped, he went on a rampage trying to get his fix. He even broke into your parents' house in a fit of withdrawal, hoping to force her to cook for him again.”
Lupin paused.
“Unfortunately, he ended up killing her by accident.”
“...”
“...Did nobody tell you about this?”