On an island on one of the lakes the Rover boys found a curious casket and this, on being opened, proved to contain some directions for locating a treasure secreted in the heart of the Adirondack Mountains.
"We must locate that treasure," said Tom Rover, and off they started for the mountains, and did locate it at last, but not before Dan Baxter had done everything in his power to locate it ahead of them.
When they finally outwitted their enemy, Dan Baxter had disappeared, and that was the last they had seen of him for some time.
The Rover boys had expected to return to Putnam Hall and their studies immediately after the winter outing in the Adirondacks, but an unexpected happening at the institution of learning made them change their plans.

Three pupils were taken down with scarlet fever, and rather than run the risk of having more taken sick, Captain Victor Putnam had closed up the Academy for the time being, and sent the pupils to their homes.
"The boys will have to go to some other school," their Aunt Martha had said, but one and another had murmured at this, for they loved Captain Putnam too well to desert him so quickly.
"Let us wait a few months," had been Dick's suggestion.
"Let us study at home," had come from Sam.
"Let us travel," Tom had put in.

"Travel broadens the mind." He loved to be "on the go" all the time.
The matter was talked over for several days, and Tom begged that they might take a trip across the continent and back, using some of the money derived from the old treasure.

At last Anderson Rover consented; and two days later the three boys were off, going by way of New York City, on the Chicago Limited.

They had spent two days in the great city by the lakes, and then come direct to the Golden Gate city.
"I wonder if we will meet anybody we know while we are out here," said Tom, as the carriage continued on its way.
"If we get down to Santa Barbara I think we'll meet somebody," answered Dick, and he blushed just a trifle.