10. To return to a human form, visualise your human self as clearly as you can. This should be sufficient, but do not panic if the transformation does not occur immediately. With practice, you will be able to slip in and out of your animal form at will, simply by visualising the creature. Advanced Animagi can transform without wands.

• • •

The moon shone onto the Black Lake, its reflection as sharp and perfect as the swollen orb in the sky. It was a clear night, though a cold one: Christmas was only a few days away. If, for some reason, a visitor found themselves standing beside a rather peculiar, gnarled tree that sat at the edge of the dark forest beyond, they would have thought at first that it was a night like any other.

Then, out of nowhere, three shadowed figures emerged out of thin air. The tallest of them laughed, his slightly hoarse voice echoing into the night. "Damn wolf's going to have no idea what hit him."

"Yeah, well, let's try not to hit him too hard," said James, as they approached the Whomping Willow. "How do you control a werewolf, anyway? There couldn't have been even one book about that? In the whole library?"

"We're unprecedented, mate," said Sirius. "One of a kind."

"It really is a good thing none of us are fleas," Peter mused. "That would probably have just made the wolf angrier."

Peter transformed then, as they had agreed, and pressed the knot in the Willow that Remus had told them about. As if on cue, Remus—not Remus—began to howl. It was a sound that chilled James' insides and refocused his mind, flooding him with purpose.

After all this time, there was finally something they could do.

James gritted his teeth as the howling gave way to snapping, snarling; he watched as the Willow shook and then froze. Rat-Peter squeaked from the mouth of the tunnel beneath it. The moon seemed to grow larger, brighter.

"Let's go," James whispered to Sirius, and together they changed, running headfirst into the darkness where their friend was waiting.