plied Madame Doisty, "near
the Esplanade des Invalides."

Lecoq had refrained from any sign of satisfaction while he was in the
jeweler's presence. But directly he had left the shop he evinced such
delirious joy that the passers-by asked themselves in amazement if
he were not mad. He did not walk, but fairly danced over the stones,
gesticulating in the most ridiculous fashion as he addressed this
triumphant monologue to the empty air: "At last," said he, "this affair
emerges from the mystery that has enshrouded it. At last I reach the
veritable actors in the drama, the exalted personages whose existence
I had suspected. Ah! Gevrol, my illustrious General! you talked about
a Russian princess, but you will be obliged to content yourself with a
simple marchioness."

But the vertigo that had seized the young detective gradually
disappeared. His good sense reasserted itself, and, looking calmly at
the situation, he felt that he should need all his presence of mind,
penetration, and sagacity to bring the expedition to a successful
finish. What course should he pursue, on entering the marchioness's
presence, in order to draw from her a full confession and to obtain full
particulars of the murder, as well as the murderer's name!

"It will be best to threaten her, to frighten her into confession,"
he soliloquized. "If I give her time for reflection, I shall learn
nothing."

He paused in his cogitations, for he had reached the residence of the
Marchioness d'Arlange--a charming mansion with a courtyard in front and
garden in the rear. Before entering, he deemed it advisable to obtain
some information concerning the inmates.

"It is here, then," he murmured, "that I am to find the solution of the
enigma! Here, behind these embroidered curtains, dwells the frightened
fugitive of the other night. What agony of fear must torture her since
she has discovered the loss of her earring!"

For more than an hour, standing under a neighbor's _porte cochere_,
Lecoq remained watching the house. He would have liked to see the
face of any one; but the time passed by and not even a shadow could
be detected behind the curtain; not even a servant passed across the
courtyard. At last, losing patience, the young detective determined to
make inquiries in the neighborhood, for he could not take a decisive
step without obtaining some knowledge of the people he was to encounter.
While wondering where he could obtain the information he required, he