Vestibule, with its unbarred window and door opening into the park.
4.

Lavatory.
5.

Stairs leading to the attic.
6.

Large and the only chimney in the pavilion, serving for the experiments of the laboratory.
The plan was drawn by Rouletabille, and I assured myself that there was not a line in it that was wanting to help to the solution of the problem then set before the police.

With the lines of this plan and the description of its parts before them, my readers will know as much as Rouletabille knew when he entered the pavilion for the first time.