Step three: while waiting for the storm, you must place your wand tip over your heart every sunrise and sundown and speak the following incantation: 'Amato Animo Animato Animagus'. If you keep repeating your incantation, there will come a time when, with the touch of the wand-tip to the chest, a second heartbeat may be sensed. Don't change anything. Keep going. Keep waiting for that storm.

Step four: As soon as lightning appears in the sky, go to the place where you've hidden your crystal phial. If you've done everything right, then you will discover a mouthful of blood-red potion inside it. Then move somewhere where you aren't going to alarm anyone or place yourself in physical danger during your transformation.

Step five: Place your wand-tip against your heart and speak the incantation 'Amato Animo Animato Animagus' and drink the potion. You will then feel fiery pain and an intense double heartbeat.

Step six: the shape of the creature into which you will shortly transform will appear in your mind. You must show no fear. It is too late now, to escape the change you have willed.

Step seven: When your transformation is complete, you are strongly advised to pick up your wand and hide it somewhere safe, so you can find it post-transformation. To return to human form, visualise your human self as clearly as you can. Do not worry if you don't change back immediately, with practice, you will be able to slip in and out of your animal form at will, simply by visualising the creature. Once you're an advanced Animagus, you should be able to transform without your wand.

"James, quit poking me!"

"Look out the window, you bloody walnut!"

I glared at him before casting my gaze to the window of the common room. My breath caught in my throat when I beheld the storm clouds.

"D'you think–"

"Maybe."

I bit my lip and twisted my fingers. After three weeks and five days of waiting, the storm was finally here.

Well, I didn't actually know if it was going to be an electrical storm. I sure hoped it was, though.

The portrait door opened, and Sirius, Peter, and Remus walked through. Remus locked eyes with me and walked over to me.

"Are you sure about this?" Remus asked softly.

"I did not hold a Mandrake leaf in my mouth for an entire month for nothing," I said.

The corner of Remus's mouth curved upwards, and he gave me a kiss. That's when thunder crackled overhead.

I let out a breath and looked to my friends.

"You can't go for it yet," James murmured. "You have to see the lightning first."

The portrait door opened again, and Lily walked through. James smiled widely and stood up to give her a hug and a kiss.

"What are you all doing at the window?" Lily asked.

"Uh... watching the storm," I said.

Lily raised an eyebrow at me but shrugged. There was another rumble of thunder, but no lightning. I crossed my fingers.

It was about ten more minutes before the first strike of lightning appeared. The moment the window lit up I was on my feet and walking towards the portrait door.

"Y/n?" Lily called. "Where are you going?"

"I, uh... the Astronomy Tower."

"Why?"

"To... watch the storm?"

"We'll come too! Sounds fun," Lily said, standing up and grabbing James's hand.

"I – uh..."

Well, that plan just fell through. They boys looked at me slightly panicked, before I came up with an idea.

"Okay, let's go," I said.

The boys looked at me confused for a moment before just playing along. We left the common room and made our way to the Astronomy Tower. Lightning arced across the sky, and everyone watched.

I grabbed Remus's hand and slowly pulled him away. Lily saw and she wiggled her eyebrows at me before turning back to the storm.

Once we were around the corner, I gave Remus a kiss.

"Now I'm gonna get this potion," I said. "Have fun explaining to Lily where I went."

Remus chuckled and kissed me again before shooing me away. I ran down the halls and up and down stairs to get to the left corridor on the seventh floor. I reached the bare space of wall where the door appeared when I was trying to hide my potion.

I need my potion now, I thought. I need it back.

The wall began rippling and the door appeared. I grabbed the handle and opened it before stepping inside excitedly.

There, in the middle of the room where I left it, was my potion. It was blood-red, like the book described. I slowly walked towards it before picking it up.

I took a deep breath.

This was it. I had no doubt that this was what I wanted to do. I'd held a Mandrake leaf in my mouth for a month, I'd whispered the incantation for three weeks and five days, I'd gone into the bloody Forbidden Forest, and I'd stolen ingredients for this.

I placed my wand tip against my heart.

"Amato Animo Animato Animagus," I whispered, before downing the potion in one gulp.

I had a moment of peace before I felt a fiery pain in my chest. I placed my hand against my heart in an attempt to stop the pain, and I felt not one, but two heartbeats. It was like an echo of the first.

I closed my eyes and waited for my animal to appear. There was nothing, so I opened my eyes, and saw a mirror in front of me. I jumped about three feet into the air and turned around on the spot. That mirror hadn't been there a moment ago.

I turned back to the mirror and looked into it. Motion tore my eyes from my reflection to something behind me. I watched in the mirror as a wolf prowled closer and closer to me. I gripped my wand in my hand.

The wolf stalked closer, before it started sprinting at me. I whirled to face it, a spell at my lips, but nothing was there. I turned back to the mirror to see not myself, but a wolf sitting where I was standing.

I immediately realised it was my Animagus form. I held my wand tightly in my hand before I felt it.

The changing.

It was like an itch, and suddenly the floor was a lot closer than before, and my hands were on the floor. Except, it wasn't my hands, it was my paws.

I let out an excited yelp and trotted around the room, testing out my new body. Walking on four legs instead of two was sightly challenging, but I quickly got used to it.

To get back to my human form, I had to visualise myself clearly. It didn't work the first few times, but I remembered that Sirius told me that it took him seventeen tries before he could transform back, so I wasn't all that worried.

I was able to transform back, and I picked up my wand before leaving this strange room.

Was I supposed to thank it? Was I supposed to sacrifice something for it?

This I Hogwarts, I thought to myself. Chill out.

Although, I supposed Hogwarts was next to a forest with a wide range of creatures, and there was a lake with a giant squid in it.

"Thank you," I murmured to the room.

Once again, like the last time I was there, the firelight seemed to flicker in amusement.