the novel doesn't say, but what i like to know is how lan bo know where to find bai chunian  it's been 3 years,  bai  might have gone anywhere, know off we think about what yan yi said, lan bo used morse code throw knocking that means lan bo might have none someone was there to help like yan yi's informent to help him, it was a big gamble lan bo took and also lan bo didn't speak or understand human english at that time so for the informent trying to speak to lan bo wound have been pointless .. so what do you guys think?..