You must also remember that Monsieur Stangerson has sworn that the door was not open." "That, however, is the only way in which it can be explained.

The Yellow Room was as closely shut as an iron safe.

To use your own expression, it was impossible for the murderer to make his escape either naturally or supernaturally.

When the room was broken into he was not there! He must, therefore, have escaped." "That does not follow." "What do you mean ?" "There was no need for him to escape--if he was not there!" "Not there!" "Evidently, not.

He could not have been there, if he were not found there." "But, what about the evidences of his presence ?" asked the President.
"That, Monsieur President, is where we have taken hold of the wrong end.
From the time Mademoiselle Stangerson shut herself in the room to the time her door was burst open, it was impossible for the murderer to escape.