On a stunning island in the South Pacific, 11-year-old Nim (Abigail Breslin) shares her world with her father, Jack Rusoe (Gerard Butler), a marine biologist who has dedicated his life to protecting her from the harsher aspects of reality after the death of her mother, Emily. The island is not just their home; it's a vibrant sanctuary filled with an array of enchanting creatures that Nim considers family, including Selkie the sea lion, Fred the bearded dragon, Chica the sea turtle, and Galileo the pelican. Jack recounts tales about Emily’s demise, claiming she was taken by a blue whale, a story that has become their shared narrative since the tragedy.
When Jack prepares to leave for a two-day scientific mission to track a newly named species of plankton called Protozoa nim, which honors Nim, she persuades him to let her remain behind to supervise Chica's egg hatching. They establish a communication link via satellite phone, ensuring Nim can reach Jack if any issues arise.
Nim escapes into the world of Alex Rover adventure novels, written by the celebrated author Alexandra Rover (Jodie Foster). A twist of fate introduces an email conversation between Nim and Alexandra, who is battling her own agoraphobia. As Nim believes she's corresponding with the adventurous Alex Rover, she shares her thoughts and feelings, enlivening her isolated existence.
Meanwhile, disaster strikes when Jack's sailboat encounters a violent cyclone, preventing him from returning to his daughter or contacting her. With danger looming, loyal Galileo steps up, fetching supplies for Jack as sharks circle the boat. On the island, Nim grows increasingly anxious, spilling her fears to Alexandra, who is still trapped in her own home.
Their peaceful routine is upended by a rowdy group of tourists arriving on a ship named The Buccaneer, which mirrors the one Nim believes took her mother away. Assuming they're pirates, she launches a series of wild tactics to scare them off, which inadvertently sets off a genuine volcanic eruption. As the tourists flee, one boy, Edmund, becomes fascinated by Nim, but his revelations about her life on the island are met with disbelief.
Inspired by her fantasies, Alexandra finally confronts her fears and embarks on a daring journey to rescue Nim. Upon reaching the island, she’s caught off-guard by Nim’s skepticism, as the girl had envisioned her hero to be the rugged Alex Rover, rather than a woman. Nevertheless, Alexandra’s determination shines through as they share a meal, gradually uniting their worlds.
Nim's heartache peaks as she questions why her father hasn't returned yet, grieving for the man she believes would have been with her if he were alive. Just when despair threatens to engulf her, Jack bursts onto the scene in dramatic fashion, windsurfing on an improvised catamaran.
The meeting of Alexandra and Jack unleashes a surprising chemistry, as Alexandra realizes that her creation reflects real-life qualities in Jack. Their journey concludes with a vibrant celebration on the beach, where laughter and connection replace loneliness. A simple coconut transforms into a playful ball, highlighting the magic of imagination and how it binds people together, capable of overcoming the toughest obstacles.
