Professor Shay initially seems like a good-hearted research historian interested in the treasure left by Angus Gunn with pure motives. However, at the end of the book, it is revealed that he is the descendant of the captain of the Argyll Queen, the boat on which Gunn served. Shay has a personal interest in finding the treasure and disguises himself as Java Jim to hide his villainy. Shay is obsessed by the treasure to the point that he frames his assistant Stebbins, who has begun to suspect that the Professor may be a criminal. Then the Professor tries a multitude of tricks and scams to beat the boys to the treasure, finally succeeding in finding the treasure but thwarted when Jupiter realizes that Shay is indeed Java Jim.