Sentence:  Stephen's craze for physical culture increased, and now it began to invade the schoolroom. Dumb-bells appeared in the schoolroom bookcases, while half worn-out gym shoes <WSD>skulked</WSD> in the corners. 
Meaning of the word marked with <WSD> tags:  To stay where one cannot be seen, conceal oneself (often in a cowardly way or with the intent of doing harm).