In nineteenth century Scotland, first mate David Gillespie quits his post on the schooner "Falcon" because of Captain Oliver's brutal treatment of the seamen, which has caused two deaths. While in a tavern, David meets engineer John Shaw, whose idea for a steamship inspires him into toiling day and night with John to create a working model, despite the protests of John's pragmatic daughter Mary. The model is a success, and David takes the drawings to London, intending to find a backer to finance a ship. He is unsuccessful, however, and becomes destitute until he runs into Junius Smith, a shipper of perishables who receives the idea with enthusiasm and hires David and John. One night, John becomes drunk and accidentally sets fire to the machine shop, destroying all their work and jeopardizing the deadline to win a commission from the Royal Navy. Smith then charters the Dog Star , a ship already equipped with a type of steam engine, and rehires David and John to alter the engine to meet their specifications. The Dog Star finally gets underway, with Mary working onboard as a stewardess. David's dream of being the captain of his own ship is dashed, however, when the Royal Navy insists upon putting their own captain aboard, and David resigns himself to working in the engine room with John. During the voyage, David and Mary confess their love for each other and agree to marry. All goes well until an exploding pipe delays their progress and mortally wounds John. After a lengthy repair in which everyone's faith is taxed, David pulls the ship through, and they arrive in New York in time. As he lies dying, John blesses David and Mary's union, and bids David to carry on his dreams.