owever, watch the departing passengers at all stops, and when
they rolled into the station at Brussels, they were certain that their
man was aboard. Nor were they mistaken. They saw him alight, look
swiftly about as though fearing that he was being followed, and then
start at a rapid pace toward the street.

Duvall went after him at once, directing Dufrenne to go to the Hotel
Metropole and secure a room in his own name, where he was to wait until
he heard from his companion. These instructions given, the detective
began to follow Seltz up the street.

The man evidently knew the town well. He made no pauses, and did not
hesitate at any time during his long walk. It terminated at a small,
third-class hotel in the older part of the city, where he went in,
entered the cafe, and selecting a table in a dim corner, ordered
breakfast.

Duvall, feeling safe in leaving him, at once sought a telephone and
proceeded to call up Dufrenne at the Hotel Metropole.

The latter, meanwhile, had turned from the railway station, and was
proceeding up the street at a leisurely pace, when a young man
approached him from behind, and touched him lightly on the shoulder.
"Monsieur Dufrenne?" he inquired, smiling.

The curio dealer glanced at the man who had accosted him, and an
answering smile lit up his face. "Oh, Lablanche, glad to see you," he
said. "I did not know you were on this case."

"Monsieur Lefevre sent me from Paris last night. We are expecting news
at any moment. Monsieur Duvall is with you, I observe."

"Yes. He is following the man from London. He will telephone me, as soon
as he learns his destination."

The man whom Dufrenne had addressed as Lablanche, looked grave. "This
affair has, we believe, been engineered by a physician here--Dr.
Hartmann--you have heard of him, of course."

Dufrenne turned to his companion. "Hartmann--the man of the stolen war
plans. _Mon Dieu!_ Why did I not think of him before?" He seemed deeply
chagrined. "Of course--of course--that explains everything."

"Where is Monsieur Duvall to communicate with you?" Dufrenne's companion
asked. His voice held a note of brisk authority.

"At the Hotel Metropole. I shall take a room there at once."

"Good. I must leave you for a short time. Await news from me at the
hotel. I shall, I hope, be able to inform you, within half an hour,
whether our suspicions regarding Dr. Hartmann are correct or not. If
they are, you will of course advise Monsieur Duvall