What Lies Beneath is a 2000 American supernatural thriller film directed by Robert Zemeckis from a screenplay by Clark Gregg, who co-wrote the story with Sarah Kernochan.

The film stars Harrison Ford as a university professor and Michelle Pfeiffer as his wife, who is unsure if their home is haunted by a ghost or if she is losing her mind.

The first film by Zemeckis' production company ImageMovers, What Lies Beneath was theatrically released in North America by DreamWorks Pictures and internationally by 20th Century Fox on July 21, 2000.

Claire Spencer and her husband Norman, an accomplished scientist and professor, live a quiet life at their lakeside home in Vermont.

She finds the bathtub filled again, sees a message stating "you know" on the foggy bathroom mirror, and her computer inexplicably types the initials "MEF".

Claire recalls a repressed memory about Norman's affair with a student named Madison, which happened during a rough patch in their marriage.

Claire leaves to spend the night with Jody, who reveals that she saw Norman arguing with a woman at a café in the nearby town of Adamant a year earlier.

Claire's suspicions return when Norman claims not to know the café in Adamant, where she sees the same necklace and jewelry box at a nearby shop.

Documentary filmmaker Sarah Kernochan had adapted a personal experience with the paranormal as a script treatment featuring a retirement aged couple dealing with restless but compassionate spirits.

[6] What Lies Beneath was filmed while production of Cast Away took a hiatus to allow Tom Hanks to lose weight and grow a beard.

[12] The New York Times wrote that "at the start, [Zemeckis] zaps us with quick, glib scares, just to show he still knows how, but his heart isn't in this kind of material anymore.

"[13] The Los Angeles Times called it "spooky with a polished kind of creepiness added in... What Lies Beneath nevertheless feels more planned than passionate, scary at points but unconvincing overall.

"[15] Empire wrote "The biggest surprise is, perhaps, that what emerges is no masterpiece, but a semi-sophisticated shocker, playfully homaging Hitchcock like a mechanical masterclass in doing 'genre'.

He praised Michelle Pfeiffer's performance, calling her "convincing and sympathetic", but commented, "Lacking a smarter screenplay, it milks the genuine skills of its actors and director for more than it deserves, and then runs off the rails in an ending more laughable than scary.