"I shall be more than comfortable. That couch is disgraceful luxury compared with what I am accustomed to when camping. May I stay, Doctor?"
Dr. Underwood's grave face relaxed into a sardonic smile.
"The house is yours!"
"Thank you! I was horribly afraid you would refuse. Is this room locked at night?"
"No."
"This door opens into a back hall, I noticed. Where does that lead?"
"To the kitchen and back stairs. Also, at the other end, to the side door of the house, opening out into the garden and to a path which runs down to the side street."
"Is that outside door locked at night?"
"Oh, yes."
"Yet--some one has been able to get into this room without detection. That could only have been at night."