Mystery Ranch - their grandpa has not got along with his sister. The children go to visit her. She takes a liking to the children and decides to leave the ranch to them. There was a friendly guy they saw on the train. He was a uranium prospector who discovered there was Uranium on the land. They set up a mine, while keeping land for the aunt. They also defeat the attempts of others to swindle the ranch from the aunt for cheep.
Mike's Mystery - The kids return a year later to find the ranch is now a big uranium mining operation. One of the swindlers returns to try to damage the ranch and take revenge on Mike who "talks to much". They are able to catch him and get Mike's mom set up in a pie making business.
Blue Bay Mystery - Grandpa takes the kids on a trip on a ship to the south seas. They do their schoolwork on the ship there. they are then dropped off on the island with Grandpa and an experienced man to spend time living and learning there. They discover another boy is on the island. He had been shipwrecked many months ago. He had lived for some time with a sailor who recently disappeared while swimming. (He may have fallen to sharks.) They take the boy back when the are picked up and are able to reunite him with his family.
Throughout the stories, the children are often able to quickly job whether a character is good or evil by looking at them. Is this a skill that has been lost as people attempt not to be prejudiced? It is an interesting line to be drawn. The kids also have a huge amount of optimism and everything seems to turn out well in the end.
