Loch Ness

At Loch Ness, Dr. Abernathy slips on rocks after glimpsing something in the loch and dies. He had managed to take a single photograph of the mysterious sight before the accident. This event marks the beginning of the hunt to confirm or debunk the Nessie myth.

Months after Abernathy's death, American zoologist Dr. John Dempsey is asked to replace him and dispel the Nessie myth. He is reluctant, having ruined his career by chasing Sasquatch. He accepts mainly for money to pay off debt and alimony, hoping the assignment will revive his standing.

Upon arriving in Scotland, Dempsey meets Dr. Adrian Foote, Abernathy's assistant who fervently believes in the monster. Foote treats the legend as fact and becomes a foil to Dempsey's skeptical approach. This meeting foreshadows the conflicting perspectives that drive the investigation.

Dempsey rents a room at a local inn run by Laura McFetridge and her daughter Isabel. Laura's warmth and Isabel's curiosity draw Dempsey into the community. The lodging becomes the base for his loch-side tests and interactions with locals.

He quickly encounters Andy McLean, a fisherman who sees Dempsey as a rival for Laura, plus the eccentric Gordon Shoals who claims ownership of the monster, and the Water Bailiff who guards the legend. The community dynamics introduce competing motives and rising tensions around the investigation. Dempsey's presence unsettles the locals and tests his resolve.

Using state-of-the-art technology, Dempsey scans the entire loch but finds no trace of the monster. He declares the end of the myth, provoking Adrian's anger as he insists on the creature's existence. Dempsey admits his own motive: to salvage his career by proving something extraordinary.

Later, Dempsey receives Abernathy's camera and discovers the photo Abernathy took the night he died, which clearly shows a dinosaur's flipper. The image challenges any quick debunking and gives Dempsey renewed purpose. He starts to believe the evidence might actually be real.

Dempsey and Adrian venture out to search the loch again and track a 40-foot-long object. The object collides with and sinks their boat, leaving Dempsey fighting for his life. He is nearly drowned but is rescued by an unseen creature and by the Water Bailiff. Following the rescue, Dempsey claims to have seen the monster.

Andy confronts Dempsey about his relationship with Laura, but Laura defends him. Isabel gives Dempsey a get-well card showing her care and belief. The incident deepens the bond between Dempsey and Isabel while highlighting tensions with Laura.

Isabel reveals to Dempsey that she has seen the creature, showing him a drawing of a water kelpie on a card. Realising the truth could lie in belief as well as science, Dempsey promises to take Isabel to the monster's home and buys her a red bicycle she has always wanted. The promise cements their growing partnership for the expedition.

Isabel leads Dempsey to a cavern beneath Urquhart Castle, where a family of plesiosaur and elasmosaur hybrids dwells. The creatures communicate with whistles that Isabel can interpret, suggesting a bridge between their world and human curiosity. Dempsey photographs the creatures, but the sight frightens them, and Isabel is knocked into the water. He rescues her, only to be confronted by the Water Bailiff.

Back at the inn, Laura ejects Dempsey in anger over the earlier betrayal, and Isabel is deeply hurt by his actions. Dempsey and Adrian then travel to London to publicly reveal the animals' existence. The trip marks a shift from private discovery to public spectacle.

On the train to London, Dempsey pleads with the Water Bailiff to stay silent, arguing that science and exposure would help the creatures. The Bailiff counters that it was Isabel's faith, not science, that first led him to the animals. The ideological clash deepens the moral stakes of the expedition.

At the Natural History Museum, Dempsey is unable to go through with the official presentation and instead swaps his photographs for Isabel's kelpie drawing. He then confesses to Adrian that he fabricated the photographs before coming to Scotland. Adrian, understanding the truth, accepts the decision and the two proceed differently from the plan. The moment marks a capitulation to belief over sensational proof.

After the conference, the Water Bailiff returns to Loch Ness and discovers that Dempsey slipped the real photographs into his bag during their train conversation. Dempsey returns to the inn and reconciles with Laura and Isabel, bringing a new red bicycle for Isabel. In the final scenes, the plesiosaurs swim through the loch with an infant, signaling a cautious coexistence between science and wonder.