For the similar sounding Harold Lloyd film of the same year, see Captain Kidds Kids.
As described in a film magazine, the grandfather of Willie Carleton Gordon put his will in a book about pirates and buried treasure, and the book is purchased by a secondhand store run by Angus MacTavish Aitken, who lives with his granddaughter Mary Pickford and a young author named Jim Gleason MacLean. After the book comes into the hands of Mary and Jim, a lawyer and the former private secretary for Carletons grandfather attempt to buy it back, but Mary has found a paper with a map showing where buried treasure may be found. Carleton agrees to share the treasure with the MacTavish crowd if they help find it. It is located at an old farm once owned by the elder Carleton, but now belongs to Lem Butterfield Hutchinson. Pretending to be geologists looking for specimens, they convince the Butterfield to allow them to dig holes all over the place. The suspicions of neighbors and the constable are aroused, and the lawyer and private secretary arrive and attempt to stop the digging. A box is found, and when opened contains a note saying that the treasure mentioned in the will is the good health Willie Carleton will have from all of the exercise spent digging. When they return to the city, it turns out that this was a test as the lawyer has been holding the Carleton fortune in trust. Mary, who bought the farm with money left to her by her mother, sells it for a profit to a man who plans to run a railroad through it. Jim Gleason sells one of his novels to a publisher, and then has the courage to ask Mary a question, which at the end she gives an answer that pleases Jim and they embrace.
Source: Wikipedia