What is wrong?

"Oh, Jon!" Mrs. Akatter, the elderly home room teacher cried. "You gave me such a fright!"
Jon quickly apologized. "Mrs. Akkater, I looking for a... a kind of a..."
He tried to think of a way that he could describe what he was looking for without sounding weird. He failed.
"Kind of a stone, a smallish one... It's very important that I find it, because... um..."
He tried to think of a really important reason why he might need to find a stone.
He failed.
But before he could go on, he noticed the old lady suddenly looking at him very oddly...
"What on Earth...?" she said, staring at him.