He could not hope to sustain his part indefinitely; sooner or later he was almost bound to betray himself, and then he would have thrown away a vital chance in mere foolhardiness.
He would betray himself, because he was not good at the charade.
mnli hypothesis: He would betray himself, because he was not good at the charade. premise: He could not hope to sustain his part indefinitely; sooner or later he was almost bound to betray himself, and then he would have thrown away a vital chance in mere foolhardiness.