“It’s quite exciting,” said Sherlock Holmes, with a yawn. “What happened next?”
“When Mrs. Charpentier paused,” the detective continued, “I saw that the whole case hung upon one point. Fixing her with my eye in a way which I always found effective with women, I asked her at what hour her son returned.
“‘I do not know,’ she answered.
“‘Not know?’
“‘No; he has a latch-key, and he let himself in.’
“‘After you went to bed?’
“‘Yes.’
“‘When did you go to bed?’
“‘About eleven.’
“‘So your son was gone at least two hours?’