Of course she was sure--and, though possible, it seemed extremely unlikely that anyone else could have discovered the hiding-place of the blue-print in the few moments that had elapsed between the time when Billy took the tray from the room and the time when the Doctor ostensibly went to find it.

A cold wave of distrust swept over her--she turned away from the Doctor silently.
Meanwhile Anderson had entered, slamming the terrace-door behind him.
"I couldn't find anybody!" he said in an irritated voice.

"I think that Jap's crazy." The Doctor began to struggle into his topcoat, avoiding any look at Dale.
"Well," he said, "I believe I've fulfilled all the legal requirements--I think I must be going." He turned toward the door but the detective halted him.
"Doctor," he said, "did you ever hear Courtleigh Fleming mention a Hidden Room in this house ?" If the Doctor started, the movement passed apparently unnoted by Anderson.

And his reply was coolly made.
"No--and I knew him rather well." "You don't think then," persisted the detective, "that such a room and the money in it could be the motive for this crime ?" The Doctor's voice grew a little curt.
"I don't believe Courtleigh Fleming robbed his own bank, if that's what you mean," he said with nicely calculated emphasis, real or feigned.
He crossed over to get his bag and spoke to Miss Cornelia.
"Well, Miss Van Gorder," he said, picking up the bag by its blackened handle, "I can't wish you a comfortable night but I can wish you a quiet one." Miss Cornelia watched him silently.

As he turned to go, she spoke.
"We're all of us a little upset, naturally," she confessed.