Jack Keane, the title character, is, quite frankly, Han Solo mixed with Indiana Jones and placed in colonial times. In trouble with some local goons, Keane needs a quick buck, so he takes a job where he has to bring a passenger to a mysterious island known as Tooth Island. His passenger is a British secret agent, and his simple errand ends up becoming an adventure where Jack will have to go up against a mad scientist and maybe learn something about his mysterious past.
The story of Jack Keane is one of the game's better aspects. I found the characters and plot enjoyable and I had no problem wanting to play through the entire thing as Jack faced evil monkeys and man-eating tea plants. There is even a bit of time where you leave Jack and control the female lead of the game, Amanda (who has a veiled past as well), adding a nice change of pace at just the right places.
One of the pleasant surprises was the inclusion of characters that aren't actually required to progress the plot or solve puzzles. There aren't a lot, but there are a good number of characters that are there for the sake of filling out the set. This is very different from most adventure games where your character is either the only one in the game, or there are so few that the plot has to explain in some way why there is no one around.