 Six-year old runaway Peter Pendleton comes across Martin s spaceship in the woods while Martin and Tim are off away doing other work for Martin s test flight. Peter actually manages to take a flight on the ship, but after Peter returns home, his family and officials believe his is just a story of fancy. That may change as Peter has taken Martin s Electro-Magnetic Neutron Converting Gravitator, on Earth an anti-gravity device. Martin has to get it back from Peter before nosy reporter Grinnell, who is already suspicious due to some coincidences, gets the truth and the device from Peter.