Henry Roth, portrayed by Adam Sandler, is a veterinarian employed at Sea Life Park in the stunning locale of Oahu, Hawaii. Known for his charms and flirtations with female tourists, he consciously steers clear of serious relationships, preferring the freedom of his bachelor lifestyle. His closest friends include Ula, a laid-back Islander played by Rob Schneider, Alexa, his androgynous German assistant, and his beloved pets, Willy the penguin and Jocko the walrus.
Henry has been diligently saving for a long-anticipated boat trip to Bristol Bay, Alaska, focused on researching walruses in their natural habitat, specifically to uncover their underwater activities, which occupy over two-thirds of their lives. However, a mishap occurs during one sailing adventure when the mast of his boat, aptly named the "Sea Serpent," breaks, forcing him to dock at a nearby shore.
While waiting for his boat to be repaired, he spends time at the Hukilau Cafe, where he meets an enchanting young woman named Lucy Whitmore, brought to life by Drew Barrymore. Instantly infatuated with her, he initially hesitates to introduce himself, fearing that Lucy might be a local. To his surprise, when he returns to the cafe the next morning, he discovers that Lucy has no recollection of their previous encounter. The cafe's owner, Sue, along with her husband Nick, reveals a startling truth: Lucy suffers from Anterograde amnesia due to a tragic car accident that occurred on her father's birthday, preventing her from forming new memories.
In a heartfelt effort to protect her, Lucy's father, Marlin, and her brother Doug, played by Sean Astin, engage in elaborate rituals to recreate that fateful day, complete with Sunday newspapers and repeated viewings of the Minnesota Vikings game. Despite warnings about her condition, Henry invites Lucy to breakfast, which spirals into a misunderstanding that leads to an emotional fallout.
Determined to see Lucy again, Henry devises clever ways to cross paths with her repeatedly, only to discover that she begins singing The Beach Boys' "Wouldn't It Be Nice" after their meetings—an encouraging sign that she might be retracing steps toward recovery. Yet, a police encounter concerning her expired car registration emphasizes the cruel reality of her condition, shattering the fragile normalcy they've built.
Henry's desire to support Lucy leads him to create a video explaining her accident and their growing bond. Although facing her history is painful for Lucy, Henry believes it’s imperative to rebuild their connection each day, helping her reconnect with past friendships and experiences. However, news that he is considering abandoning his plans for Alaska to focus on her leads Lucy to a painful decision to erase him entirely from her life.
As departure time nears, Henry is informed by Marlin that Lucy has adjusted to life at a brain injury institute and is even teaching art, bringing a bittersweet vibe to his plans to leave. Feeling hopeful, he races to see her, only to learn that while she may not remember him, she holds vivid dreams of him and has painted numerous portraits.
In a heartwarming resolution, Lucy wakes up one day to find a tape labeled "Good Morning Lucy." It recounts her past while culminating in a moment that reveals their wedding. In a happy twist, she ultimately finds herself on Henry's boat, now sailing in beautiful Alaska, ready to embrace her life with her husband and their daughter, Nicole.
