Alexander Hartdegen (GUY PEARCE) is a first-year associate professor at New York City's Columbia University in the late 1890s who's so busy and preoccupied with his work, experiments and theorems that he needs to be reminded by his associate, Dr. David Philby (MARK ADDY), that he's to propose to his girlfriend, Emma (SIENNA GUILLORY), that night, a point that causes his housekeeper, Mrs. Watchit (PHYLLIDA LAW), to tidy him up.
Despite his habitual lateness and distractions, Emma agrees, but finds herself the immediate victim of a robbery gone bad. Four years later, and still obsessed by the disastrous turn of events, Alexander has built a time machine that he plans to use to travel back in time, prevent Emma's death, and then allow things to play out the way they should have. Unfortunately, Alexander learns that you can't mess with time and has his quest thwarted.
He thus sets out to explore the future and lands in the year 2030 where he encounters Vox (ORLANDO JONES), an all-knowing library "protonic" linked to all of the databases of the world. Despite this fascinating find, Alexander sets out further into the future, hoping to find an answer as to why he can't change the past. A freak accident, however, leaves him unconscious with his machine sending him far into the future.
He eventually arrives in the year 802,701 where seemingly primitive, cliff-dwelling people known as the Eloi live. Two of them, Mara (SAMANTHA MUMBA), a young adult woman, and Kalen (OMERO MUMBA), a younger boy, have managed to learn how to speak English, and try to explain their ways to Alexander. As he tries to figure out this world that's so foreign from the one he left, he soon learns why there are no adults among the Eloi.
It turns out another savage race of beings, the subterranean Morlocks, feed upon the Eloi and occasionally pop out for some quick raids on the peaceful people. After they abduct Mara, Alexander then sets out to rescue her, eventually causing him to encounter their all-knowing leader, the Uber-Morlock (JEREMY IRONS).