The World War still rages on in Europe, and Tom Swift is still inventing wartime technology, but inspiration comes in the form of infatuation: while taking Mary Nestor for a brief flight, he is unable to communicate due to the noise of the engine, which sets Tom onto the track of developing a totally silent airship. While Mary Nestor was the spark, Tom intends to offer this to the United States government for use on the western front.
While this is still a germ of an idea, Tom is approached by Mr. Gale and Mr. Ware, representatives of the Universal Flying Machine Company, a competing airship manufacturer. Tom is offered a lucrative salary to join the firm, but Tom is disinterested in the money. Tom's refusal infuriates the men, and events are set in motion, which include the (accidental) kidnapping of Mr. Nestor, Mary's father.
Tom builds a special silencer for airship engines. The silencer consists of several components: a new type of propeller, retooling the engine compression, but most importantly, a new type of muffler. The muffler system is simply described as a series of baffles. The end result is an airship which produces no discernible noise, to be used on scouting missions in the war.