Then he saw Mrs.Marlow look out, and she glanced right and left about her.

The next instant, she emerged from the room with the same stealthiness, closed and locked the door with a key which she immediately pocketed, slipped along the corridor, and disappeared into Franklin Fullaway's suite.

It was all over in less than a minute, and Allerdyke turned into his own door, smiling cynically to himself.
"She looked right and left, but she forgot to look up!" he muttered.
"Ah! those small details.

And what does that mean?
Anyway, I know which door she came out of!" He glanced at his watch--precisely half-past eleven.

He made a note of the time in his pocket-book and went to bed.