Harry flung himself out from behind the bush and pulled out his wand.
“EXPECTO PATRONUM!” he yelled.
And out of the end of his wand burst, not a shapeless cloud of mist, but a blinding, dazzling, silver animal. He screwed up his eyes, trying to see what it was. It looked like a horse. It was galloping silently away from him, across the black surface of the lake. He saw it lower its head and charge at the swarming Dementors… Now it was galloping around and around the black shapes on the ground, and the Dementors were falling back, scattering, retreating into the darkness… They were gone.
The Patronus turned. It was cantering back toward Harry across the still surface of the water. It wasn’t a horse. It wasn’t a unicorn, either. It was a stag. It was shining brightly as the moon above… it was coming back to him…
It stopped on the bank. Its hooves made no mark on the soft ground as it stared at Harry with its large, silver eyes. Slowly, it bowed its antlered head. And Harry realized…
“Prongs,” he whispered.
But as his trembling fingertips stretched toward the creature, it vanished.
Harry stood there, hand still outstretched. Then, with a great leap of his heart, he heard hooves behind him—he whirled around and saw Hermione dashing toward him, dragging Buckbeak behind her.
“What did you do?” she said fiercely. “You said you were only going to keep a lookout!”
“I just saved all our lives…” said Harry. “Get behind here—behind this bush—I’ll explain.”
Hermione listened to what had just happened with her mouth open yet again.
“Did anyone see you?”
“Yes, haven’t you been listening? I saw me but I thought I was my dad! It’s okay!”
“Harry, I can’t believe it… You conjured up a Patronus that drove away all those Dementors! That’s very, very advanced magic.”
“I knew I could do it this time,” said Harry, “because I’d already done it… Does that make sense?”
“I don’t know—Harry, look at Snape!”
Together they peered around the bush at the other bank. Snape had regained consciousness. He was conjuring stretchers and lifting the limp forms of Harry, Hermione, and Black onto them. A fourth stretcher, no doubt bearing Ron, was already floating at his side. Then, wand held out in front of him, he moved them away toward the castle.
“Right, it’s nearly time,” said Hermione tensely, looking at her watch. “We’ve got about forty five minutes until Dumbledore locks the door to the hospital wing. We’ve got to rescue Sirius and get back into the ward before anybody realizes we’re missing…”