Sentence:  He and Rebecca then found a secluded boardinghouse to which Will and Susannah would move on Monday. Before the westbound left on Saturday morning, McCaleb spent a few minutes alone with Will. “You'll be released from here Monday,” ... Don't <WSD>let any grass grow under your feet</WSD> in Cheyenne; once you're there, head for Box Elder Creek.” 
Meaning of the word marked with <WSD> tags:  To settle in one place rather than moving to another.