The film begins with the daring explorer Sir Lionel Frost, Hugh Jackman, embarking on an adventurous journey alongside his loyal partner, Mr. Lint, played by David Walliams. Their quest takes them to the mysterious depths of a lake, where they encounter the legendary Loch Ness Monster. Using a lasso, Lionel manages to capture a photograph of the creature, but the celebration is short-lived as the beast unexpectedly seizes Mr. Lint with its powerful jaws and drags him beneath the surface of the water. Determined to save his friend, Lionel dives into the water, risking everything, but their boat ends up destroyed after the monster whips its tail in a defensive attack, adding chaos to the already perilous situation.
Following this harrowing event, Lionel returns to London, where his partner Mr. Lint decides to leave their partnership. The constant danger and Lionel’s apparent indifference toward those he takes along leave Mr. Lint disillusioned. As Lionel sorts through his correspondence, he comes across an invitation that challenges him to provide proof of the existence of Sasquatch—a creature he believes he can find. Among his belongings, he also discovers a large footprint, which he firmly believes is proof of the elusive creature.
Eager to prove himself and finally gain recognition, Lionel presents his findings at the prestigious Optimates Club, a society comprised of notable men dedicated to groundbreaking discoveries. However, due to his past lack of concrete evidence, he has been repeatedly rejected by the club’s members. The club’s rigid and dismissive leader, Lord Piggot-Dunceby, played by Stephen Fry, dismisses Lionel outright, even breaking the footprint he brought as proof. Undeterred, Lionel boldly challenges the society, asserting that he will find the Sasquatch and prove his worth. Impressed by his resolve, piggot-Dunceby agrees to let Lionel join if he succeeds—though secretly, the leader plans to sabotage him. Meanwhile, Piggot-Dunceby enlists a bounty hunter, Willard Stenk, played by Timothy Olyphant, with orders to eliminate Lionel should he pose a threat to their reputation.
Lionel’s expedition takes him to Old Kemp Creek, where he ventures into the forest and astonishingly encounters the Sasquatch-like creature. To his surprise, the creature is not only capable of speech but also reads and writes. This creature, who introduces himself as Mr. Link, explains that he sent the invitation to Lionel, having seen his earlier newspaper articles. Aware of Lionel’s reputation, Mr. Link reveals that he longs for companionship, fearing loneliness among the other creatures like himself, who live in remote regions. He asks Lionel for help in locating a place called the Himalayas, believing that the climactic mountains hold other beings like himself, possibly Yeti, which could mean the chance for friendship and understanding. Realizing the importance of safety, Lionel decides to disguise Mr. Link to pass unnoticed through busy crowds, affectionately naming him ‘Susan’ after a kind prospector he once saw.
Together, Lionel and Mr. Link set off on a journey filled with danger and discovery. Their first stop is to find a map held by Lionel’s late friend, Aldous Fortnight, and his widow, Adelina, played by Zoe Saldana. Upon reaching her, Lionel’s intentions are solely focused on obtaining the map, but Adelina is cold and dismissive, resenting Lionel for missing Aldous’s funeral and refusing to assist him. Later, when they attempt to steal the map from Adelina’s home, their plans are foiled when the safe containing the map is accidentally shot out of the window by her butler, providing Lionel with an opportunity. The trio narrowly escapes by disguising themselves as nuns at the train station, but they are soon spotted by Stenk and his men, leading to a chaotic fight that spills into the station. Despite the danger, they manage to flee, with Adelina warming up to Mr. Link, showing kindness and curiosity about his quest for Shangri-La, where potentially the Yeti reside.
The group then embarks on a sea voyage, during which Lionel warns Mr. Link of the danger posed by Stenk, emphasizing his own obsession with winning a wager. Their relationship faces moments of tension, but Adelina begins to question Lionel’s selfish attitude, especially when Mr. Link, affectionately called Susan, demonstrates genuine kindness. After some introspection, Lionel names the creature ‘Susan,’ recalling a moment when a prospector smiled at him instead of running away, inspiring this new identity. Their journey continues through India, where they seek out a guide named Gamu, played by [Ching Valdez-Aran]. His granddaughter, Ama, played by [Amrita Acharia], finds them and takes them to Gamu’s home. Things get complicated when Gamu’s granddaughter inadvertently reveals their presence, and Gamu himself is revealed to be a beast, causing Ama to faint. Nonetheless, she provides the direction they need toward the mountains where the Yeti are believed to live.
Their expedition finally reaches Shangri-La, but their arrival isn’t unnoticed. They are captured by the Yeti and brought before the Yeti Elder, played by Emma Thompson, who perceives Susan as a distant cousin and therefore unworthy of acceptance in their community. The Elder orders her soldiers to imprison the humans in a pit. Down there, Susan feels rejection and loneliness, questioning his own identity, while Lionel and Adelina confront their own differences and doubts. “You’re a friend, and that makes you special,” Adelina tells Susan, encouraging him. With the help of the Yeti, they manage to escape, but not without a chase that culminates on an icy bridge. There, Lord Piggot-Dunceby and his men arrive, intending to kill Susan and silence the evidence of his existence. In a final act of defiance, Lionel confronts Piggot-Dunceby, asserting that Susan is his friend and that he no longer cares about the club or its shallow rules.
As the bridge is violently shattered, chaos erupts. Piggot-Dunceby falls to his death, and Mr. Collick, Piggot-Dunceby’s assistant, meets a similar fate. Meanwhile, Stenk, still obsessed with capturing Susan, tries to kill everyone but ends up hanging onto an icicle. Lionel pulls him down, leading to a slap-fight, which ends when Stenk falls onto a sharp piece of ice, meeting his doom. After escaping the chaos, the heroes look back at Susan, who playfully blows a raspberry at the Elder, highlighting their bond. As the adventure wraps up, Lionel makes a move to pursue a romantic relationship with Adelina, but she chooses to leave and live her own life, seeking her own adventures.
In a heartfelt conclusion, Lionel invites Susan, now a true friend, to join him on future expeditions. The film closes with a touching scene of Lionel and Susan in London, captured in a framed photo, symbolizing their newfound friendship and the endless possibilities ahead.
