Sentence:  With his mouth <WSD>agape</WSD> and his hands clenched, Rufus Dawes, incapable of further speech, made a last effort to nod assent, but his head fell upon his breast; the next moment, the flickering light, the gloomy prison, the eager face of the doctor, and the astonished face of Vickers, vanished from before his straining eyes. 
Meaning of the word marked with <WSD> tags:  Wide open.