Harry got to his feet, feeling nervous. They faced each other with the desk between them.
“You may use your wand to attempt to disarm me, or defend yourself in any other way you can think of,” said Snape.
“And what are you going to do?” Harry asked, eyeing Snape’s wand apprehensively.
“I am about to attempt to break into your mind,” said Snape softly. “We are going to see how well you resist. I have been told that you have already shown aptitude at resisting the Imperius Curse. You will find that similar powers are needed for this… brace yourself, now. Legilimens!”
Snape had struck before Harry was ready, before he had even begun to summon any force of resistance. The office swam in front of his eyes and vanished; image after image was racing through his mind like a flickering film so vivid it blinded him to his surroundings.
He was five, watching Dudley riding a new red bicycle, and his heart was bursting with jealousy… he was nine, and Ripper the bulldog was chasing him up a tree and the Dursleys were laughing below on the lawn… he was sitting under the Sorting Hat, and it was telling him he would do well in Slytherin… Hermione was lying in the hospital wing, her face covered with thick black hair… a hundred Dementors were closing in on him beside the dark lake… Cho Chang was drawing nearer to him under the mistletoe…
No, said a voice inside Harry’s head, as the memory of Cho drew nearer, you’re not watching that, you’re not watching it, it’s private—
He felt a sharp pain in his knee. Snape’s office had come back into view and he realised that he had fallen to the floor; one of his knees had collided painfully with the leg of Snape’s desk. He looked up at Snape, who had lowered his wand and was rubbing his wrist. There was an angry weal there, like a scorch mark.
“Did you mean to produce a Stinging Hex?” asked Snape coolly.
“No,” said Harry bitterly, getting up from the floor.
“I thought not,” said Snape, watching him closely. “You let me get in too far. You lost control.”
“Did you see everything I saw?” Harry asked, unsure whether he wanted to hear the answer.
“Flashes of it,” said Snape, his lip curling. “To whom did the dog belong?”
“My Aunt Marge,” Harry muttered, hating Snape.
“Well, for a first attempt that was not as poor as it might have been,” said Snape, raising his wand once more. “You managed to stop me eventually, though you wasted time and energy shouting. You must remain focused. Repel me with your brain and you will not need to resort to your wand.”
“I’m trying,” said Harry angrily, “but you’re not telling me how!”
“Manners, Potter,” said Snape dangerously. “Now, I want you to close your eyes.”