as alarmed as was the young valet. But Muller's
cheeks were flushed and a flash of secret joy, of pleasurable
expectation, brightened his deep-set, grey eyes. He sat quite
motionless, but every nerve in his body was alive and tingling. The
humble-looking little man had become quite another and a decidedly
interesting person. He laid his thin, nervous hand on the carriage door.

"We are not there yet," said the commissioner.

"No, but it's the third house from here," replied Muller.

"You know where everybody lives, don't you?" smiled Horn.

"Nearly everybody," answered Muller gently, as the cab stopped before
an attractive little villa surrounded by its own garden, as were most of
the houses in this quiet, aristocratic part of the town.

The house was two stories high, but the upper windows were closed and
tightly curtained. This upper story was the apartment occupied by
the owner of the house, who was now in Italy with his invalid wife.
Otherwise the dainty little villa, built in the fashionable Nuremberg
style, with heavy wooden doors and lozenged-paned windows, had no
occupants except Professor Fellner and his servant. With its graceful
outlines and well-planned garden, the dwelling had a most attractive
appearance. Opposite it was the broad avenue known as the Promenade, and
beyond this were open fields. To the right and to the left were similar
villas in their gardens.

Dummel opened the door and the three men entered the house. The
commissioner and the valet went in first, Muller following them more
slowly. His sharp eyes glanced quickly over the coloured tiles of the
flooring, over the white steps and the carpeted hallway beyond. Once he
bent quickly and picked up something, then he walked on with his usual
quiet manner, out of which every trace of excitement had now vanished.

The dull winter sun seemed only to make the gloom of the dark vestibule
more visible. Johann turned up the light, and Horn, who had visited the
Professor several times and knew the situation of the rooms, went
at once to the heavy, carved and iron trimmed door of the study. He
attempted to open the door, but it resisted all pressure. The heavy
key was in the inner side of the big lock with its medieval iron
ornamentation. But the key was turned so that the lower part of the lock
was free, a round opening of unusual size. Horn made sure of this by
holding a lighted match to the door.

"You are right," he said to the valet, "the door