The tree house detectives' green thumbs are tested as they attempt to grow award-winning plants for the upcoming fair. The tree house becomes a green house as the detectives experiment with soil, light, plant life cycles, and genetics to grow the perfect plant.
As Bianca and Kali arrive to meet the rest of the tree house detectives at the NASA auditorium for an awards ceremony, they learn that Dr. D, Jacob, and Katherine are having minor traffic problems. Convinced that they have plenty of time to get to the ceremony, and with not much else to do while they sit and wait, the detectives decide to work on their latest school project. The assignment is to come up with an idea for what transportation will look like in 100 years.
One afternoon, the tree house detectives feel their tree house shake. They wonder what could have caused the vibration. Unsure whether they had just experienced an earthquake, the tree house detectives decide to make the unexplained vibration the subject of their next case and set out to solve The Case of the Shaky Quake.
The tree house detectives' Global Positioning System (GPS) devices begin to act up. To solve the mystery, they learn about electricity, magnetism, electromagnetic waves, the Earth's atmosphere, aurora, and magnetic storms.
In this program, students are invited to actively join the tree house detectives as they investigate the Case of the Unknown Stink. The tree house detectives accept the challenge of trying to find the source of an unpleasant odor that is invading the surrounding neighborhoods. To determine the source of the stink, the detectives learn about the sense of smell: what it is, how people and animals smell, and how wind speed and direction influence the movement of odor. They also learn that the source of the unknown stink is right under their very noses.
The tree house detectives' efforts to raise money with a car wash dry up when the city is hit with water restrictions. With the help of Problem-Based Learning (PBL), the entire group learns all about the water cycle, the water table, global climates, and much more to get the project flowing again.
Travel back in time with the tree house detectives to learn about invention from Orville and Wilbur Wright. The detectives try to create their own invention and get help from the Wright brothers, NASA researchers, and others.