anchor: I was not sure then if Inglethorp was the criminal or not, but if he was I reasoned that he would not have the paper on him, but would have hidden it somewhere, and by enlisting the sympathy of the household I could effectually prevent his destroying it. 
positive: I was unclear at that point as to whether or not the criminal was Inglethorp.
negative: I knew with absolute certainty then that Inglethorp was definitely the criminal.