Now, let me just run over the course of events, and you will contradict me if I go wrong." The man sat huddled up in his chair, with his head sunk upon his breast, like one who is utterly crushed.

Holmes stuck his feet up on the corner of the mantelpiece and, leaning back with his hands in his pockets, began talking, rather to himself, as it seemed, than to us.
"The man married a woman very much older than himself for her money," said he, "and he enjoyed the use of the money of the daughter as long as she lived with them.

It was a considerable sum, for people in their position, and the loss of it would have made a serious difference.

It was worth an effort to preserve it.
The daughter was of a good, amiable disposition, but affectionate and warm-hearted in her ways, so that it was evident that with her fair personal advantages, and her little income, she would not be allowed to remain single long.

Now her marriage would mean, of course, the loss of a hundred a year, so what does her stepfather do to prevent it?
He takes the obvious course of keeping her at home and forbidding her to seek the company of people of her own age.