Sentence:  Certain portions of the conversation of the talkative old clerk, which had wearied me at the time, now recurred to my memory with a new significance; and a suspicion crossed my mind <WSD>darkly</WSD>, which had not occurred to me while I was in the vestry. 
Meaning of the word marked with <WSD> tags:  Mysteriously; forebodingly, ominously.