The Secrets of the Sea Chest is the fourth book in the Fribble Mouse Library Mystery series. It is spring when Fribble's family receives an invitation to come vacation at Great Uncle Skipper's house on the coast of Maine. Great Uncle Skipper also says he is mailing to Fribble his old sea chest that is filled with all kinds of secrets. It is also the time when Fribble must write a report on careers, in the present, past or future. Once Fribble receives and opens the sea chest and begins to examine its contents, he decides he will make his school report on sailors of the past. Fribble leans many things as he uses library research skills to study objects like scrimshaw, a barometer and a telescope, and as he learns about signal flags at sea and how to tie sailor knots. After a successful Career Night at school, Fribble and his family journey with the special treasure map that Great Uncle Skipper has sent them to visit him in Maine and seek the treasure.