Chester lives with his Grandma, his cat Mr. Pickles and Simon the ghost. Simon and Chester are best friends. Their attic is the location for some of the best activities known to humankind: making up songs about passersby, acting out scenes from Simon's exciting Dr. Darington novels and creating the incredible Treat-A-Matic snack dispenser.

But Chester has also befriended a non-ghost named Amie, and she is coming over to work on their science fair project. Amie has a surprising idea for this project, and Simon and Chester's friendship will be put to the test as a result. Will Simon behave? Will Amie come between the two friends? Will an invisible Simon make fart noises that Chester has to explain? All will be revealed . . .