This arrangement was agreed on. Dave took the train, and reached Croydon about dusk. He found it to be a busy little manufacturing city near the coast. From what Mr. King had written him, and through some inquiries, Dave was soon on his way to the so-called aerodrome, where the giant airship was being built.
An old roofless molding shop had been utilized for the construction. It looked lonely and deserted as Dave came up to it. The windows were boarded up, apparently to keep out prying eyes. The big front doors were closely padlocked, and a temporary canvas roof was in place.
The street lamps of the city ran out to the factory, and nearby were some houses. Dave felt sure that Mr. King and the others had taken living quarters in the vicinity. He had no doubt that a little inquiry would result in locating them.
Dave walked around the old plant, thinking a good deal of the proud hopes that attached to the big airship inside. The upper pair of windows of the place were not boarded up. Dave’s eyes chanced to be scanning these as he was about to cross the street to where the houses were.
“Hello!” he cried out sharply, in a startled way.
A sudden flash, bright and dazzling, shot across the whole row of windows from the interior of the building. It resembled the illumination made by a sudden powder blast, but there was no report.
“Why, what can that be?” exclaimed the bewildered young aviator.
Dave bent his ear and listened. No sound broke the stillness. He could not figure out the circumstances for the moment. He was puzzled, and yet reluctant to leave the spot without learning what the mysterious flash portended.
“Someone!” spoke Dave, suddenly.
Then he broke into a run. Mystery had become suspicion. Against the light of a corner lamp, he saw, away down the length of the building, the outlines of a ladder. Its top rested on the sill of one of the upper windows.