veral detectives were
out looking for it. It was almost nightfall when Amster ran breathlessly
into room number seven. "I have him! he's waiting outside across the
way!" This was Amster's report.

Muller threw on his coat hastily. "You didn't pay him, did you? On
a cold day like this the drivers don't like to wait long in any one
place."

"No danger. I haven't money enough for that," replied Amster with a
sad smile. Muller did not hear him as he was already outside. But
the commissioner with whom he had been talking and to whom Muller had
already spoken of his voluntary assistant, entered into a conversation
with Amster, and said to him finally: "I will take it upon myself to
guarantee your future, if you are ready to enter the secret service
under Muller's orders. If you wish to do this you can stay right on now,
for I think we will need you in this case."

Amster bowed in agreement. His life had been troubled, his reputation
darkened by no fault of his own, and the work he was doing now had
awakened, an interest and an ability that he did not know he possessed.
He was more than glad to accept the offer made by the official.

Muller was already across the street and had laid his hand upon the door
of the cab when the driver turned to him and said crossly, "Some one
else has ordered me. But I am not going to wait in this cold, get in if
you want to."

"All right. Now tell me first where you drove to last evening with the
sick lady and her companion?" The man looked astonished but found his
tongue again in a moment. "And who are you?" he asked calmly.

"We will tell you that upstairs in the police station," answered Muller
equally calmly, and ordered the man to drive through the gateway into
the inner courtyard. He himself got into the wagon, and in the course
of the short drive he had made a discovery. He had found a tiny glass
stopper, such as is used in perfume bottles. He could understand from
this why the odour of perfume which had now become familiar to him was
still so strong inside the old cab. Also why it was so strong on the
delicate handkerchief. Asta Langen had taken the stopper from the bottle
in her pocket, so as to leave a trail of odour behind her.

CHAPTER THREE. THE LONELY COTTAGE

Fifteen minutes after the driver had made his report to Commissioner
Von Mayringen, the latter with Amster entered another cab. A well-armed
policeman mounted the box of this second vehicle. "Follow that cab