“What motive can you possibly have for thus endeavouring to ally yourself with me?” I inquired, without attempting to disguise my suspicion.
“A secret one.”
“For your own ends, of course?”
“Not exactly. For our mutual interests. By my own action in taking you in when you were knocked down by the cab I have placed your life in serious jeopardy; therefore, it is only just that I should now seek to rescue you. Yet if I do so without first obtaining your promise of silence and of assistance, I may, for aught I know, bring an overwhelming catastrophe upon myself.”
“You assure me, upon your honour as a woman, that no harm shall befall me if I carry out the instructions in those mysterious letters?”
“If you obey without seeking to elucidate their mystery, or the identity of their sender, no harm shall come to you,” she answered solemnly.
“And regarding the silence which you seek to impose upon me? May I not explain my adventures to my friend, in order to account for the blood upon my clothes and the injury to my head?”
“Only if you find it actually necessary. Recollect, however, that no statement whatever must be made to the police. You must give an undertaking never to divulge to them one single word of what occurred last night.”
There was a dead silence, broken only by the lapping of water, which had already risen and had flooded the chamber to the depth of about two inches. The place was a veritable death-trap, for, being a kind of cellar and below high-water mark, the Thames flood entered by a hole near the floor too small to permit the escape of a man, and would rise until it reached the roof.
“Come,” she urged at last. “Give me your undertaking, and let us at once get away from this horrible place.”