A scientist tries to prove the existence of the Loch Ness monster.
Dr. Dempsey, an American scientist who has become a skeptic after a disastrous wrong call, isn't exactly enthusiastic to be sent by his well-funded employer to Scotland to (dis)prove the existence of the Loch Ness monster, but has no choice. He finds the locals stubborn, "primitive" and all but hospitable, not in the least because the Nessie legend is the only tourist attraction, but still gets romantically attracted by his independent inn-keeper Laura, and both her kid and his enthusiastic local assistant end up making him face a small family of Nessie-dinosaurs, but is this to be made public?—KGF Vissers
A scientist tries to dis-prove the existence of the Loch Ness monster in the remote Scottish region. But in end ends up believing in it and caring for it so much that he gives up lifetime of fame to protect the mystery and to be with the woman he now loved (the innkeeper at Loch Ness)
Opening on a pub near Loch Ness, a scientist named Dr. Abernathy steps out for some air. Standing on the shore of the Loch, he sees something rise from the water. Astonished, he takes a single photograph before slipping and falling on the rocks, killing him.
A short time later in Los Angeles, disgruntled freshman college tutor, Dr. Jonathan Dempsey (Ted Danson), is obligated to journey to Scotland to replace Dr. Abernathy, who was searching for the Loch Ness Monster. Dempsey is reluctant to do so, as he ruined his respected zoology career after a fruitless three-year search for the Sasquatch and is now considered a joke among his colleagues. The only reason he agrees to go is because he is broke and cannot pay alimony to his demanding ex-wife, Caroline, whom he once named a newly discovered species of wasp after.
Dempsey travels to Scotland and reluctantly begins on a Cryptozoology mission along with Adrian Foote (James Frain), former assistant to Dr. Abernathy and an eager young Scottish man who fanatically believes in the existence of the creature. Dempsey repeatedly claims there is no mystery, and that the monster is just a hoax created by the locals of Loch Ness to support their economy. Jonathan books into a small inn and meets his grouchy landlady, Laura McFetridge (Joely Richardson), and her nine-year-old daughter, Isabel, who quickly grows close to Jonathan.
Jonathan quickly finds himself in hot water with the locals, in particular one named Andy McLean (Nick Brimble), who sees Dempsey as a rival for the affections of Laura. The water bailiff, (Ian Holm), guardian and protector of Loch Ness, does all he can to ensure that Dempsey fails in his search and leaves the Loch empty-handed. After the sonar equipment is sabotaged by the locals, Dempsey confronts the water bailiff, who insists that the mystery of Loch Ness will never be destroyed. Dempsey challenges him to "come out and watch him". After scanning the entire Loch and finding nothing, Dempsey declares it is the end of the Loch Ness monster, leaving Adrian crushed, but the subsequent argument between them ends on a slightly re-conciliatory note when Dempsey tells Adrian that, despite his skepticism, he did want to find the monster.
Throughout the film, Laura overcomes her initial dislike of Dempsey, and they quickly grow attracted to each other. Isabel possesses a second sight and is able to foretell certain things, such as her mother's growing affection for Dempsey. The day before Dempsey's departure from Loch Ness, Adrian brings him the remainder of Dr. Abernathy's possessions, including his camera. The next morning Adrian is awakened by Dempsey, who says they are going back out for another sweep of the Loch. He reveals that after developing the pictures on Abernathy's camera, the last picture on the roll shows a large, rhomboid shaped flipper submerging into the water. After tracking a 40 ft object chasing a school of salmon, it collides with the boat, sinking it and sending Dempsey and Adrian into water.
Dempsey nearly drowns but somehow surfaces after a large dark object is seen moving in the water behind his quickly sinking body. After returning to the inn, he his ecstatic, claiming to have seen the creature while under the water. After Dempsey is beaten up by Andy McLean for "moving in on his woman", Isabel makes him a get-well card which features a drawing of what she calls a "water Kelpie." Dempsey realizes that Isabel, too, has seen the monster, as her drawing of the creature's fins are identical to the picture taken by Abernathy. After Dempsey promises to buy her the red bicycle that she has always wanted, Isabel agrees to show him the monster.
Later that day, Isabel leads Dempsey to an underground cavern beneath Urquhart Castle and warns him not to use lights as it scares the creatures. After a startling encounter with some sea otters, Dempsey prepares to leave, humiliated. Suddenly a Plesiosaur rises from the water and Isabel is shown to know it very well, even being able to communicate with it through a series of whistle-like calls. Responding to the calls, a second creature appears, the two animals apparently being mates. While in an astonished euphoria, Dempsey ignores Isabel's warnings and takes a photograph, the flash alarming the creatures, causing them to dive back into the water and cause havoc. Isabel falls into the water and almost drowns, and Dempsey is saved by the furious water bailiff.
Dempsey develops the photographs and faces Laura's wrath about him using Isabel and nearly getting her killed. Laura refuses to have anything to do with Dempsey or his discovery of the monster, despite his claims that when he reveals the existence of the creatures, Laura's business will boom as people from all over the world come to the Loch to see the monsters. Laura evicts Jonathan and Isabel is deeply hurt that Dempsey used her in such a way. Upset, but not about to give up his chance at vindication, he leaves for London to attend a press conference where he plans to reveal the photos of the monsters to the world.
The water bailiff follows him on the train, imploring him not to reveal the truth of Loch Ness. Dempsey insists that exposure will be best for the creatures, claiming that science will be able to care for the creatures professionally. Scornful, the water bailiff points out the irony in that it was not science that helped his "discovery", but a little girl. He also reminds Dempsey of the harm done to the planet because of science, and that these creatures have survived unaided since before the ice age.
At the conference, Dempsey is unable to go through with it and replaces the real photos with Isabel's drawing of the "kelpie", causing an uproar while he discreetly leaves. On the way out, he tells a baffled Adrian that he had the pictures made by computer before he ever came to Scotland. Adrian, knowing the truth, understandingly plays along. Meanwhile, on a bus headed back to Loch Ness, the water bailiff discovers the pictures inside his suitcase and is moved almost to the point of tears. Dempsey returns to the inn and reunites with Laura, along with the red bicycle he promised Isabel. In Loch Ness, the Plesiosaur pair is seen swimming underwater with a baby alongside.
