"Abroad the Lady Jane, in New Zealand waters long ago, was a perky young cabin boy named Bob Bobstay. Ben's ship was about to leave for China, but he was allowed to go ashore to visit Hone Heke the chief's son. They decide to paddle up a river in Hone's canoe in search of eels ... then Ben discovers an "emerald cave" and rushes back to tell his friends from the Lady Jane. Unknown to Ben he is overheard by two villians, Ezechial 'ingepin and Boston Bill who proceed to get up to no good. In the end the varmints get their just deserts and Ben learns all about emeralds" --Back cover.