During the film's opening sequence, we encounter a man, likely Einstein (played by Walter Matthau), skillfully playing the violin. As he performs, another man walks by a poster that advertises Boyd's comet. We then shift our focus to Catherine Boyd (portrayed by Meg Ryan) who is with her fiancé, James Moreland (Stephen Fry). Catherine is deeply engrossed in calculations related to the comet, but when she tries to share a story, James dismissively comments that she's "babbling." The narrative alternates between this scene and a heated debate among a group of older gentlemen about the existence of time.
As Catherine and James cruise around in a convertible, they encounter engine trouble. Meanwhile, Einstein engages in lively discussions with his elderly friends, leading to his iconic assertion, > "I do not believe God plays dice with the universe." The couple arrives at a garage where Ed Walters (played by Tim Robbins) is embroiled in an argument with his boss, Bob (Tony Shalhoub), about diagnosing the car's issues based solely on sounds.
When Bob sends Ed to check on the couple's vehicle, he mistakenly assumes they hail from Princeton College. Upon meeting Catherine, Ed immediately feels a connection. James, with a sense of entitlement, obnoxiously inquires about someone who can service a British engine. Ed charmingly asks, "May I look under the bonnet?" This seems to impress James, who permits Ed to inspect the vehicle. After examining it, Ed jokingly states, "You have no spark," a remark that cleverly alludes to the chemistry—or lack thereof—between Catherine and James. As she presses for more information, Ed whimsically adds, "My guess is that you have a short stroke and premature ignition." Despite her feigned innocence, it’s evident that Catherine understands the double entendre.
To appease James, Ed claims the repairs will take several days, prompting Catherine to call a cab and inadvertently leave behind a cherished pocket watch. At this moment, viewers catch a glimpse of a hand discreetly moving the watch under some magazines, leaving questions lingering about intent—was it an accident or a deliberate act? This theme of happenstance versus intentional actions recurs throughout the film.
After finding the watch, Ed learns that the address on the watch leads to the home of Albert Einstein, who happens to be Catherine's uncle. Assisting Einstein and his friends in retrieving a badminton racket, Ed forms a bond with them, making his admiration for Catherine apparent. Noting that his niece appears dissatisfied with her fiancé, Einstein contemplates ways to assist Ed in winning her affection. Understanding that Catherine prefers very intelligent partners, Ed jokingly remarks, "That's easy, lend me your brain for a couple of days." This sparks a clever idea in Einstein's mind.
Together with his companions, Einstein devises a scheme to convince Catherine that Ed has made groundbreaking advancements in cold fusion, allowing him to power a rocket destined for the stars, thereby capturing her interest. They assist Ed in masquerading as a genius by helping him present a paper on cold fusion at a symposium, as well as facilitating his success on an IQ test conducted by Catherine's fiancé. As a mathematician, Catherine becomes intrigued yet confounded by the complexities of "Ed's" cold fusion theory. Although Ed yearns to confess his deception to Catherine, he struggles to find the right moment.
Throughout the course of the film, Einstein and his friends meddle in Catherine's relationship with James and actively encourage Ed. James is portrayed as a sadistic individual who subtly demeans Catherine. Despite the obstacles, the story ultimately progresses toward a classic happy ending, incorporating elements such as an appearance by President Eisenhower, a dazzling convertible, a motorcycle, waltz music and a comet, all of which contribute to this charming romantic tale.
