“Why?”

Mr. Grimm was peering through the inscrutable darkness, straight into her face—­a white daub in the gloom, shapeless, indistinct.

“I have known Madame Boissegur for half a dozen years,” Miss Thorne continued, in explanation.  “We have been friends that long.  I met her first in Tokio, later in Berlin, and within a few weeks, here in Washington.  You see I have traveled in the time I have been an agent for my government.  Well, Madame Boissegur received this letter about half-past four o’clock this afternoon; and about half-past five she sent for me and placed it in my hands, together with all the singular details following upon the ambassador’s disappearance.  So, it would seem that you and I are allies for this once, and the problem is already solved.  There merely remains the task of finding and releasing the ambassador.”

Mr. Grimm sat perfectly still.

“And why,” he asked slowly, “are you here now?”

“For the same reason that you are here,” she replied readily, “to see for myself if the—­the person who twice came here at night—­once for the ambassador’s letters and once for his cigarettes—­would, by any chance, make another trip.  I knew you were here, of course.”

“You knew I was here,” repeated Mr. Grimm musingly.  “And, may I—?”

“Just as you knew that I, or some one, at least, had entered this house a few minutes ago,” she interrupted.  “The automobile horn outside was a signal, wasn’t it?  Hastings was in the car?  Or was it Blair or Johnson?”

Mr. Grimm did not say.

“Didn’t you anticipate any personal danger when you entered?” he queried instead.  “Weren’t you afraid I might shoot?”

“No.”

There was a long silence.  Mr. Grimm still sat with his elbows on his knees, staring, staring at the vague white splotch which was Miss Thorne’s face and bare neck.  One of her white arms hung at her side like a pallid serpent, and her hand was at rest on the seat of the couch.

“It seems, Miss Thorne,” he said at length, casually, quite casually, “that our paths of duty are inextricably tangled.  Twice previously we have met under circumstances that were more than strange, and now—­this!  Whatever injustice I may have done you in the past by my suspicions has, I hope, been forgiven; and in each instance we were able to work side by side toward a conclusion.  I am wondering now if this singular affair will take a similar course.”

He paused.  Miss Thorne started to speak, but he silenced her with a slight gesture of his hand.

“It is only fair to you to say that we—­that is, the Secret Service—­have learned many things about you,” he resumed in the same casual tone.  “We have, through our foreign agents, traced you step by step from Rome to Washington.  We know that you are, in a way, a representative of a sovereign of Europe; we know that you were on a secret mission to the Spanish court, perhaps for this sovereign, and remained in Madrid for a month; we know that from there you went to Paris, also on a secret mission—­perhaps the same—­and remained there for three weeks; we know that you met diplomatic agents of those governments later in London.  We know all this; we know the manner of your coming to this country; of your coming to Washington.  But we don’t know why you are here.”