On January 5, 1900 in London, four friends arrive for a dinner at the house of their friend H. George Wells (Rod Taylor), an inventor. Bedraggled and exhausted, George arrives and begins to describe the strange experiences he has had since the group last met.
At their earlier dinner, on December 31, 1899, George describes time as "the fourth dimension" to David Filby (Alan Young), Dr. Philip Hillyer (Sebastian Cabot), Anthony Bridewell (Tom Helmore), and Walter Kemp (Whit Bissell). He shows them a small model of his time machine and asks a guest to press a tiny lever. The device disappears, validating his claim, but his friends remain unconvinced; their reactions vary from curiosity to frank dismissal.