"What can I do?"
"I will tell you. For a long time we have tried to get one of our own agents into Dr. Hartmann's house, but without success. He is very shrewd—very cautious. All his servants are countrymen of his, upon whom he knows he can depend. His patients are people of wealth, position, standing, who, he knows, could not possibly be agents of the French police. He will take no others, and always insists upon the strictest references. It is for these reasons that we have failed. Now an opportunity presents itself for you, mademoiselle, to accomplish that which the police cannot accomplish. You are an American girl, of prominent family, of wealth, of position. I am informed that your aunt, by her second marriage, was the Countess d'Este. Should you apply to Dr. Hartmann for treatment, you will have no difficulty in obtaining admission, for he could not, by any chance, think that Miss Grace Ellicott, of New York, was in the employ of the French secret police. You observe, mademoiselle, Monsieur the Prefect's object in sending you to Brussels?"
Grace nodded. She was beginning to feel a keen interest in the matter. "But I am not ill," she said, with a laugh. "How can I ask Dr. Hartmann to treat me?"
"We have thought of that. The matter has been under consideration ever since we were advised, early this afternoon, that you were coming. We have thought it best that you represent yourself to the doctor as a somnambulist."
"A sleep walker?"
"Precisely. It is a form of nervous trouble which is by no means infrequent. We are informed that Dr. Hartmann has treated several such cases in the past. There are not symptoms, except a state of nervousness on the part of the patient which in your case it is probable the excitement of the enterprise will supply, and, of course, the tendency to walking in the sleep. This latter you must assume."
"Assume?"
"Yes. You must pretend to be a somnambulist. You must get up, each night, at some hour, and wander about the house—pretending to be oblivious of all about you. You are not normally conscious. You are in a walking dream. Your eyes are fixed ahead—seeing no one. It will not be difficult for you to pretend all this—and naturally, by wandering about in this way, you may—we hope you will—have excellent opportunities to observe what goes on within the doctor's walls."
"Is that all I am to do—just watch?"
"I think not. If we are unable, by other means, to prevent the stolen box from being delivered to Dr. Hartmann, it must be recovered from him, at any cost—at any cost whatever—" the woman repeated, significantly. "Even life itself cannot be spared, in this case. The box must be recovered, no matter what the price we pay—so we are informed by Monsieur Lefevre."