Picture this.
A rich man is driving on a freeway in his Ferrari. Suddenly, a huge Basilisk (mythical snake-like creature) comes out of nowhere and swallows him.
He blacks out, but 10 minutes later he wakes up, realising he was inside the stomach of the creature, although at the time he did not know what it was.
So then his wife call him, & he answers:
"Honey, can i call you back, I'm in the middle of something."
*explanation*: when one says he is in the middle of something, he usually means he is busy, though in this case, as he was in the middle (stomach) of the Basilisk, and he didn't know what the creature was at the time, he had called it "Something".
Understand?