“See, Watson!” said he. “ ‘High red house with stone facings.’ There is the signal station all right. We know the place, and we know the code; so surely our task should be simple. There’s a ‘to let’ card in that window. It is evidently an empty flat to which the confederate has access. Well, Mrs. Warren, what now?”

“I have it all ready for you. If you will both come up and leave your boots below on the landing, I’ll put you there now.”