six o'clock
`` Why , '' resumed Darrow , `` how , if Monsieur X was a hundred miles or so away , as Eldridge figured , did he know that McCarthy had not obeyed him ? We must suppose , from the probable fact of that knowledge , that either Monsieur X had an accomplice who was keeping him informed , or he must be near enough to get the information himself . '' `` There is a third possibility , '' broke in Jack . `` Monsieur X might have sent along his ` sign ' at six o'clock , anyhow , just for general results . '' Darrow nodded his approval . `` Good boy , Jack , '' said he . `` That is just the point I could not be sure about .