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.