On the very night H.G. Wells (Malcolm McDowell) reveals his time machine to his dinner guests, the police come looking for one of them (David Warner), because they’ve just found out that he’s Jack the Ripper. Since McDowell has conveniently explained how to operate his time machine, Warner has no trouble escaping into the future. And when the device returns automatically to Wells’s basement, McDowell hastens in pursuit in order to protect what he assumes will be a crime-free socialist utopia in 1979 from the evil he’s inadvertently helped deliver.
Of course, there’s no obvious reason he couldn’t have taken a few days or weeks or months to make plans and preparations, then traveled — or better yet, sent a police officer — to a point a few days earlier than Warner’s destination in order to ambush him as he arrives and save everybody lots of trouble, not to mention prevent several murders. But then we’d have a shorter movie.
McDowell soon finds himself in San Francisco, because that’s where his time machine is being exhibited along with other Wells artifacts. When he converts some pounds to dollars at a bank, he realizes Warner must have had to do the same thing, so he goes from bank to bank until he meets charming Mary Steenburgen, who not only remembers changing money for Warner but thinks McDowell is cute.
McDowell searches for Warner while simultaneously falling in love with Steenburgen and amusing the audience by his attempts to deal with all the novelties of 1979. Eventually he has to save Steenburgen from Jack the Ripper, confess his love to her, and head back home to write all those books he saw mentioned in the Wells exhibit.
The plot is a mass of contrivance, coincidence, plot holes, and weird inconsistencies. For one minor example of the last, the time machine is said to be solar powered, but it runs just fine despite never being in sunlight the whole movie.
But as with any number of films, the plot flaws are at least partly redeemed by likable characters. McDowell’s and Steenburgen’s genuine mutual chemistry and affection — in real life they got married shortly after the movie was made — carry the film. For that matter, Warner makes a decent melodramatic villain, the sort you’d like to hiss at. It's not a classic film, but it's quite tolerable.