Having his guests gathered at his house for their weekly Thursday dinner, the Time Traveler begins to expound on his theory with regard Time which will redefine the notion of Time and Space as they know it. When Filby, one of the Time Traveler’s guests, wonders if the Time Traveler is being a tad presumptuous, the Time Traveler assures Filby that anon he and rest will have no choice but to admit the Time Traveler’s theory about the nature of Time is infallible.
Subsequently, the Time Traveler expounds on the current notions of Space which is believed to have three dimensions: length, width, and thickness. He mentions the current mathematical attempts to discover a fourth dimension of Space, the theory of which is that there might be an additional right angle to the preexisting three right angles if we only knew where to look or how to perceive Space in a way other than the way to which we are currently limited to. It is then the Time Traveler reveals his discovery: He asserts that Time, and not an additional, spatial right angle, is the fourth dimension of Space. Moreover, just as man has found a way to defy gravity and vertically travel through Space via the balloon, the Time Traveler claims that he has found a way to travel through time.
At this point, his guests are understandably pessimistic. So the Time Traveler excuses himself and returns with a cubic object the size of a small clock. He sets it on a table and explains that he had just finished constructing it and that this is only the miniature model of the real thing whose construction is nearly complete in his laboratory. To show that there is no sleight of hand involved, the Time Traveler has everyone draw near before he has one of his guests, the Psychologist, push the lever. Consequently, the cubic object disappears, presumably traveling through time.
The Psychologist deduces that the object must have traveled into the past, arguing that if it traveled into the future that the object would be still visible on the table. The Narrator, who is also one of the Time Traveler’s guests, argues, however, that if it had traveled into the past then the object should have been on the table last Thursday night, the Thursday night before that, and so on. Consequently, the Psychologist attributes its invisibility to the the speed with which it is traveling through time, arguing that the speed has endowed it with a physical property commensurate to its speed—not unlike like a fired bullet which is invisible to the naked eye.
Presently, the Medical Man, another of the Time Traveler’s guests, argues that though they are astounded now that by morning they will all come to their senses. Subsequently, to show that he is in earnest, the Time Traveler shows his guests the real thing, the life size model of the time machine in his laboratory. When the Medical Man wonders if this all just a hoax, the Time Traveler assures him and the rest of his guests that when the preparations are complete, he—the Time Traveler—will indeed travel through Time with his time machine.