There are lots of people going in and out.

He must have dropped the ear-rings out of his pocket when he stood behind the door, and did not notice he dropped them, because he had other things to think of.

The jewel-case is a conclusive proof that he did stand there....

That's how I explain it." "Too clever! No, my boy, you're too clever.

That beats everything." "But, why, why ?" "Why, because everything fits too well...