He nodded again, his keen eyes full of fire, turned, ascended the steps, and pulled the bell.
Mary sighed heavily as she bent her weary steps, for the fifth time, up the basement stairs to answer his imperative summons.
"Is your mistress at home?" Mr. Rider inquired, in a quick, business-like tone.
"Yes, sir; but she is engaged with callers," the girl replied.
"So much the better," returned the detective; then, bending a stern look on her, he continued: "I am an officer; I have business in this house; you are to let me in and say nothing to any one. Do you understand?"
Mary grew pale at this, and fell back a step or two from the door, frightened at the term "officer."
Mr. Rider took instant advantage of the situation and stepped within the hall.
"Don't dare to mention that I am here until I give you leave," he commanded, authoritatively, and then ran nimbly and quietly up stairs.
It was the work of but a moment to find the room where Mona was confined, turn the key, and enter.
"What does this mean, Miss Richards?" he asked, regarding her curiously.
"How do you happen to be locked up like a naughty child?"