"Dear me! how shocking! you make my flesh creep. And do you really think that this Dr. Duncan is doing the same?" asked Susan, much amused at the old woman's folly.
"No, no, Miss, don't go away and think I believe that," Mrs. Harris exclaimed in alarm; "all I say is that it's strange—very strange indeed."
"And what do the servants think about it?"
"They think that there's something wrong here," and she tapped her forehead. "The maid says she's got the horrors like. She's very afraid about her baby; she seems to think that there's some harm coming to it; she won't let it out of her sight, and when anyone comes into the room, she starts and trembles fearful. They say, Miss, that it's just as if she had a delusion that everyone wanted to murder the child. Now that ain't natural like, allowing for all a mother's affection."
"It is indeed very strange," said Susan musingly; "but I must not waste your time any longer, Mrs. Harris—I am a sad gossip. Good morning to you, I will see you again soon."
So this was Mary's vulnerable point. Susan had suspected as much. She fancied that it would not be very difficult to make use of this extreme anxiety of the mother for her child.
As she came out of the shop she noticed an old woman, shabbily dressed in black and much bent with age, tottering feebly along the pavement on the opposite side of the street with a large basket on her arm.
Had Susan kept her eyes as open as usual during these expeditions to St. John's Wood, she would have observed, before this, that she herself was not the only person who was acting the detective round Dr. Duncan's house. On nearly every occasion that she had come to the neighbourhood, the shabby old woman had been there too, dogging her footsteps, watching her movements unsuspected, spying the spy.
Susan had contrived to discover that Dr. Duncan was in the habit every Saturday of visiting a patient who lived a considerable way out of London. Failing, as I have said, with all her cleverness, to mature a definite plan of action, she determined to risk all, and call boldly on Mary while her husband was away on the following Saturday.
She had a great confidence in her luck; she felt that something would turn up to favour her purpose, if she once gained admittance into the house. Knowing Mary as she did, she considered that it would not be difficult to terrify her again into her former crazed state.