What does Holmes’ examination of the will indicate?

Holmes is gone until around one o'clock in the afternoon. When he returns to Baker Street he tells Watson what he has learned from reading the will of Helen Stoner's mother.

“I have seen the will of the deceased wife,” said he. “To determine its exact meaning I have been obliged to work out the present prices of the investments with which it is concerned. The total income, which at the time of the wife's death was little short of £1100, is now, through the fall in agricultural prices, not more than £750. Each daughter can claim an income of £250, in case of marriage. It is evident, therefore, that if both girls had married, this beauty would have had a mere pittance, while even one of them would cripple him to a very serious extent. My morning's work has not been wasted, since it has proved that he has the very strongest motives for standing in the way of anything of the sort.

Evidently Dr. Roylott could retain the capital from the inheritance but would have to pay either daughter 250 pounds a year out of the income. If both daughters married, he would be left with an annual income of only 250 pounds. This is strong evidence that he must have murdered Julia Stoner to keep her from being married and that he intends to murder Helen, who is engaged to be married very soon. Watson writes that Helen came to see Holmes in early April of 1883, and Helen tells them that she and Percy Armitage are to be married "in the course of the spring."

It would seem advisable for Dr. Roylott to wait at least a little while before trying to kill Helen after she has consulted the famous Sherlock Holmes, but he is under time pressure. He has no idea what Holmes might advise Helen to do. The detective has the option of moving Helen to the home of her aunt, Miss Honoria Westphail, who lives near Harrow, where his client would be out of her stepfather's reach. This is why Holmes wants to go to Stoke Moran that very afternoon. He tells Helen, "Yet we have not a moment to lose." And he tells Watson, "...this is too serious for dawdling, especially as the old man is aware that we are interesting ourselves in his affairs." The whole case is wrapped up in one day. Helen arrives early in the morning, and Dr. Roylott is dead, bitten by his own poisonous snake at around three-thirty the next morning. 

The story shows the dependent position of women in Victorian times. Dr. Roylott can keep the entire income of 750 pounds a year while his stepdaughters are living under his roof. But once either girl marries she will have a man to handle her affairs, and her husband can see to it that Roylott pays him the one-third of his annual income. Helen's long story to Sherlock Holmes and Dr. Watson indicates that Roylott's big house at Stoke Moran is not only heavily mortgaged but in bad need of repairs. He must be desperate. He couldn't sell the big place in its run-down condition, and he couldn't keep up with the mortgage payments. He is being forced to go ahead with his plan to kill Helen even though he should know it would be wise to lie low until the detective became involved with other affairs. Roylott tries to have his snake kill Helen that very night, but Holmes and Watson are waiting in her bedroom and have sent her to sleep in safety in her old bedroom at the end of the corridor.