Sentence:  But after the doctor 's return that <WSD>night</WSD> Alex could see , from the high window in his own room , the now familiar figure crouched on a truly impressive heap of towels , apparently giving its egg hatching powers one final chance before it was replaced in its office by a sure-enough hen . 
Meaning of the word marked with <WSD> tags:  the time after sunset and before sunrise while it is dark outside