And as Allerdyke turned back to his own room, the third event of that day happened, and seemed to him to be the most surprising and important one of all.
What made Allerdyke pause as he retraced his steps along the corridor, pause to look over the balustrade to the floor immediately below his own, he never knew nor could explain.

But, just as he was about to re-enter his room, he did so pause, leaning over the railings and looking down for a moment.

In that moment he saw Mrs.Marlow.
A considerable portion of the floor immediately beneath him was fully exposed to the view of any one leaning over the balustrade as Allerdyke did.

This was a quiet part of the hotel, a sort of wing cut away from the main building; the floor at which he was looking was given up to private suites of rooms, one of them, a larger one than the others, being Fullaway's, which filled one side of the corridor; the others were suites of two, in some cases of three rooms.

As he looked over and down, Allerdyke suddenly saw a door open in one of these smaller suites--open silently and stealthily.