Havoc by E. Phillips Oppenheim

The Square was a small one, and in a particularly unsavory neighborhood. Laverick, who had once visited his partner's somewhat extensive suite of rooms in Jermyn Street, rang the bell doubtfully. The door was opened almost at once, not by a servant but by a young lady who was obviously expecting him. Before he could open his lips to frame an inquiry, she had closed the door behind him.

"Will you please come this way? " she said timidly.