The story concerns mischievous mythical creatures, the Gremlins of the title, often invoked by Royal Air Force pilots as an explanation of mechanical troubles and mishaps. In Dahl's book, the gremlins' motivation for sabotaging British aircraft is revenge of the destruction of their forest home, which was razed to make way for an aircraft factory. The principal character in the book, Gus, has his Hawker Hurricane fighter destroyed over the English Channel by a gremlin, but is able to convince the gremlins as they parachute into the water that they should join forces against a common enemy, Hitler and the Nazis, rather than fight each other.
Eventually, the gremlins are re-trained by the Royal Air Force to repair rather than sabotage aircraft, and restore Gus to active flight status after a particularly severe crash.[Note 3] The book also contains picturesque details about the ordinary lives of gremlins: baby gremlins, for instance, are known as widgets, and females as fifinellas, a name taken from the great "flying" filly racehorse Fifinella, that won both the Epsom Derby and Epsom Oaks in 1916, the year Dahl was born.