C830 (5)
Yeh Xin's presence and voice are undetectable, so the leader won't suspect anything. He can't imagine Yeh Xin is still alive, and as long as Yeh Xin's situation remains hidden, there's a plausible excuse for him to escape scrutiny. The events from 26 years ago are now beyond verification, and without Yeh Xin's exposure, it's just his word against nothing, leaving no room for investigation
