Sentence:  The foregoing , aided by several clues I 'll withhold to <WSD>keep</WSD> you on your toes , will pursue you with a tenacity worthy of Inspector Javert , but before they close in , gird yourselves , I repeat , for a vengeance infinitely more pitiless . 
Meaning of the word marked with <WSD> tags:  keep in a certain state, position, or activity; e.g., "keep clean"