Tris struck fast, but Quirrell's reaction was every bit as quick.
The instant Tris raised his hand, Quirrell raised his too and fired a Disarming Charm of his own. The red light of the two spells collided in midair. They held for only a moment before Tris's spell was overwhelmed.
Quirrell's Disarming Charm shot toward Tris without losing any of its power.
Tris reacted even faster than Quirrell. Seeing that he couldn't win a head-on clash of spells, he rolled across the floor, narrowly avoiding the Disarming Charm, then fired an Impact Curse while shouting, "What are you standing around for? Do something!"
The three younger children were still in a daze.
Quirrell's appearance had already left them bewildered, and Tris's sudden attack had been even harder to process.
Even after Tris spoke, Hermione and Ron still hesitated.
Attacking a professor required rather more mental preparation. Though they had known on the way here that they might face a professor and had braced themselves for it, all that preparation had been directed at Snape.
Now that their opponent had changed, they had to start over.
This was where the difference showed.
Harry was just as stunned and confused, but he was the first to react after Tris spoke. With a flick of his wand, he sent an Impact Curse flying.
He didn't understand why Quirrell was here, but whoever appeared in this place could only be after the Philosopher's Stone!
Then let's take him down first.
Four against one, the advantage is mine! Harry thought.
Then, in less than three minutes, all four children had been stripped of their wands, trussed up like parcels, and propped upright in front of the magic mirror.
The gap in their abilities was slightly larger than expected.
Apart from Lockhart in the story's second