NOTE: This spoiler was sent in by Pook! who says... "This is a great movie, just the right blend of wacky Adam Sandler-ness and true touching and romantic moments :)"
As the movie opens several women are telling friends and family about the amazing romance they just had in Hawaii. They are all very different, a very tan girl, an African-American woman working in a salon, a businesswoman, a firewoman, even an overweight older woman in her 50's, and all of them are talking about how they were swept off their feet by a charming local that they had a one-night stand with. But then the next day he couldn't see them anymore, and each one has a different reason why - he was married, he was gay, etc. They all say that it was Henry Roth.
We meet Henry Roth (Adam Sandler) who is explaining to yet another woman that he is really a secret agent and has endangered his mission by revealing too much to her. He says he has to go and jumps off the pier onto a moving jetski, and when the man driving it asks what he's doing he says that he'll pay him to just keep going. We shortly learn that he's really a veterinarian at a Sea World type park in Hawaii, as he's stitching up the side of his native friend Ula (Rob Schneider) who was attacked by a shark. Ula is constantly followed by his numerous children, who are videotaping him. Ula plies Henry for details, saying that he lives vicariously through him. Henry explains in a roundabout way that he's commitment-phobic, so one night stands with tourist women are all he can handle. Suddenly Henry's assistant, a lanky and mannish Swedish woman named Alexa, comes running in, shouting that there's a problem. The aquarium's walrus is sick. Henry makes Alexa dive into the water to test the temperature and into a barrel to get fish from the bottom, and then when he gives the walrus the Heimlich maneuver the walrus expels gallons of vomit all over Alexa, who seems unbothered. She leaves, and then Henry reveals that he did it just to get revenge over her eating his lunch, dancing around with a penguin.
Later he's riding on his own sailboat which looks old-fashioned and wooden.
He's talking to himself about his plans to sail to Alaska to study the walruses when the mast of the ship snaps in half and falls off. He takes a small motorboat back to land, where he winds up in a small cafe run by a large native woman named Susie (Amy Hill) and her brother Nick. They apparently sell a lot of Spam in the cafe. Henry is waiting for the Coast Guard to come tow his boat when a light is flashed in his eyes. He looks over and sees that it's the sun reflected off a knife held by a beautiful girl (Drew Barrymore) sitting at another table, who's building a volcano out of her waffle. He goes back to the aquarium, where he talks to Alexa about an old girlfriend in college who dumped him for her college advisor (another woman) which made him afraid of relationships. Alexa admits that she's grumpy because she hasn't gotten laid lately and offers Henry the chance to get naked with her in his office. He says he isn't into men.
The next day he goes to the cafe and there the beautiful girl is again, this time building a house out of her waffle, but she seems stumped by the door. Henry comes over to her table and offers her a toothpick to use to make a door hinge and she notes that his hands smell like fish. He's embarrassed about it, but she says that she likes it because her father and brother are fishermen. She introduces herself as Lucy and says that she's an art teacher at the local Middle School. Henry tells the truth about his job for once, and they flirt and get to know each other. As they're leaving they both end up doing happy "I met someone really neat" dances but when another car between theirs pulls away they each see the other dancing and are shy about it. They make tentative plans to see each other again the next day, since that day she says is her father's birthday and they're going to pick a pineapple, a tradition that they have.
Henry goes golfing with Ula and his kids, and Ula says that he got the phone number of a woman for Henry who's leaving the next day but wants to hook up with someone before that. He talks about Lucy but Ula seems startled that he'd go out with a local. Henry starts to say that he's not interested, and then hits his golf ball over a cliff. He climbs down and finds Lucy down on the beach, and she says that she came to see him and can't wait to see him that day...and the next day...and the next day...Henry starts to freak out, and it turns out that he was knocked unconscious by the golf ball and was just imagining it. He agrees to go see the woman Ula was trying to get him together with.
He's out with the woman, a bubbly blonde who quickly downs a huge drink and who obviously wants to go home with him, but he finds that he's still thinking about Lucy. He confesses that their drinks were non-alchoholic and that he often seduces women just in town on vacation and then makes excuses not to see them again. The woman asks if they can pretend he didn't just say that and sleep together anyway, but he declines and refers her to Alexa, who is sitting at the bar.
It's pouring rain the next day as he gets to the cafe and as soon as Susie spots him going to talk to Lucy she tells him that she needs to talk to him, but is distracted by another customer. He sits down and starts to talk about his walrus and how his hands smell like fish, but it all comes off sounding like crude innuendo and Lucy starts to freak out, calling for Nick to help her. Nick comes at Henry with a meat cleaver and Susie pulls him outside to tell him that Lucy has no short-term memory. She was Lucy's mother's best friend, so she and Nick look out for her along with Lucy's father and brother. Lucy was in a car accident while riding with her father over a year ago on his birthday to get a pineapple. Her father only had a few broken ribs, but she had a head injury that makes it so that when she sleeps at night she forgets everything that happened the day before. All her memories before that are fine, though, even though she still thinks every day that it's her father's birthday. Henry asks why she hasn't noticed the day in the newspaper, but Susie says that her father has had hundreds of special ones made up from the day of her accident and they go through the same things with her every day to keep up the illusion that everything is fine.
Lucy wakes up the next day and tells her father (Blake Clark) happy birthday! He already has a pineapple and she's disappointed, but he says he has something else for her to do - he's just painted his workshop, but it's too white, so he wants her to paint him a picture on the walls. She tells him to relax and watch the Vikings game. As she goes out to paint, her father and brother (Sean Astin) a spastic bodybuilder on steroids with a bad lisp wearily take out a video of the game to put on. Lucy finishes the painting and makes her father a pineapple upside down cake, then gives him a present - a video of The Sixth Sense. She asks them if they want to watch it and they agree. As they're going off to bed she exclaims that she couldn't believe the ending and it was such a surprise. She goes to her room, and then her father and brother share a resolved look. They go and toss out the extra cake, take a new pineapple out of the freezer, wash the clothes she wore that day, re-wrap the video, and her father takes pictures of the mural she painted in the workshop. Then he and her brother take paint rollers and paint the wall white again.
Henry is talking to Ula about Lucy as they work on his ship, and Ula says that it sounds like she's the perfect girl for him - they can have fun, and then the next day she won't remember anything so he won't need to come up with weak excuses to not see her again. He protests that it's evil, and then Ula falls through the deck of the ship. Henry can't get Lucy off his mind, though, so he goes back to the cafe. Nick says that he's supposed to threaten him with a meat cleaver if he comes back, but Henry bets him $20 that he can get Lucy to talk to him again. Nick takes him up on it and he goes and makes Lucy a door for her waffle house again, but this time she's irritated, asking if he comes from a planet where it's okay to touch other people's food. The next day he tells Nick to make it double or nothing, and this time he tries sitting with her but she brushes him off again, pretending she doesn't speak English. There's a whole montage of her dismissing him in various ways, until finally he pretends to cry while trying to read the menu. She asks him what's wrong and he sobs that he can't read. She tries to help him and they start to leave together, but then he remembers his vision where she was getting clingy with him and decides to leave. She asks him why he's suddenly not interested after pretending to not be able to read, and he realizes that she knew it was a put-on and tries to cover for himself, which makes her hurt and angry. She drives home and he follows her, guilty that he made her feel bad, but her father and brother come out to threaten him to stay away. They say if he goes back to cafe that they'll have Nick get him with the meat cleaver.
Henry talks to Alexa about this at work, and asks if she went out with the tourist from the other night. Alexa says she decided she wanted a "sausage" more than a "taco." She advises Henry to follow the letter of what Lucy's father said and not see her...at the CAFE. Henry starts to stake out the road between the cafe and Lucy's house, coming up with all kinds of reasons to make her stop and talk to him including getting a jump for his car, to stop a pretend robbery by Ula who Lucy attacks with a baseball bat, and to see a penguin on the road that he brought from the aquarium although Lucy doesn't and drives over it - fortunately not harming it. They flirt and talk and get to know each other better each time, until finally one day he has himself tied up like someone was trying to kidnap him. He sees that the car approaching isn't hers, though, and sits up, and sees that it's Lucy's father and brother. They say that once he's done with his fake kidnapping to come to the house. He does, and he asks what brought about their change of heart. The father tells him to look into the workshop where Lucy is painting while singing (badly) to "Wouldn't It Be Nice" by the Beach Boys. He tells Henry that he noticed that she only sings on days when she's seen him, to songs that her mother used to listen to with him.
The next day he goes to the cafe to meet her again since now her father hasn't forbidden it, but Lucy catches sight of a cop writing her a ticket for expired registration. Lucy says that her registration doesn't expire until next year, but the cop points out the real date. Lucy grabs a newspaper and confirms the correct date and is confused and devastated. She races home and Henry races after her. As soon as she starts to pull up Lucy's father announces that it's a "bad day" as if this has happened before and we see him explain the newspapers and the accident to her. She runs outside and starts to sob and shout. They hand her a portfolio of pictures of her from the accident, a newspaper article on it and other documents from the hospital and doctor. She says that she needs to talk to the doctor to confirm it but her father says that she already has, many times, on other "bad days" when they had to explain everything to her. She insists on going anyway. On the way there, she asks why Henry is there and her father tells her that they are dating. Henry apologizes for not being better-looking. Lucy asks if they're sleeping together and everyone looks at him, and Henry says that they haven't, but that they want to.
They go to the head trauma and memory clinic where her doctor Dr. Keats (Dan Akroyd) confirms that from CAT scans they just did her condition hasn't improved and is most likely permanent. She has inoperable scar tissue that is preventing her short-term memories from converting to long-term memories. He says that it could be worse, though, she could be like Ten Second Tom. He introduces them to Ten Second Tom (Allen Covert), who can only remember things for ten seconds and is constantly introducing himself. Her brother also asks Dr. Keats if his "friend" was using steroids if it would cause wet dreams, which his "friend" has been having a lot lately.
They all go home and Lucy is starting to come to terms with her condition. She thanks Henry for being so kind to her and tells him the next day to talk to her about lilies, she's crazy about them. Henry talks to her father about why they have to hide everything every day, and that there wouldn't be "bad days" if they were just up front about her condition, but her father doesn't seem to think it's a good idea.
The next day Henry shows up with a bouquet of lilies for Lucy and a present "from a secret admirer."
The present turns out to be a video tape that sums up world events from the last year like the Martha Stewart trial and Arnold Scwarzenegger becoming governor, and also her condition. She is torn up about it, but less so than the day before it seems. She goes outside to think about it and Henry says to her father that it's taken her about an hour to adjust to the idea, and now she can try to see her friends and go on with her life. Henry and Lucy start dating more formally, with her watching the tape every day and re-adjusting to the world. They go to a barbecue with her old friends who are all very happy to see her. One of her friends (Maya Rudolph) is now married and pregnant and gets irritated with her husband for not being as romantic as Henry who has to get Lucy to fall in love with him again every single day. Henry and Lucy walk on the beach, and she videotapes him and asks if he loves her. He waffles for a bit and then admits that he does, probably more than anyone has ever loved anyone else in the world. They kiss, and she sighs that first kisses are always the best.
They date and kiss several more times, and each time she comments about how first kisses are the best. He starts to put more serious moves on her at the aquarium and she says that they just met, but he says that they've made out about 23 times now so if they average it out, it's like making out twelve times and so he's entitled to free boob access. They go out and see the walrus and Lucy asks the walrus if she should go to bed with Henry, and Henry gets the walrus to nod yes.
They go back to his room and are watched first by dolphins, then by Ula swimming in the dolphin tank. The next day he composes a song for her about how she's "Forgetful Lucy" and how much he loves her, and they go back to her house where they are falling asleep together. He warns her not to, and then sleepily asks her to marry him. She says that of course she will, and they fall asleep.
The next morning they wake up and see each other, and she screams. She starts to attack him and he says that they're together, otherwise how would he know that she likes lilies and Beach Boys songs? She calls him a stalker and beans him with her baseball bat. Her father and brother come to his rescue and the Dr. Keats comes out and confirms that they're all right. Lucy is upstairs, and she overhears Henry talking about his dream to sail to Alaska for a year to study the walruses, but how he doesn't want to leave since it seems like Lucy is making progress and is almost remembering him. The doctor says he just thinks that because he wants to and her father says he should just go. Lucy is very saddened by hearing them talk. She goes out to see Henry later and tells him that she loves him, and that she wants to break up. She says that it's not fair that he doesn't have time to do anything but get her to fall in love with him every day and that she wants him to go to Alaska. He protests, saying that she agreed to marry him but she asks him what kind of future could they have? She asks him if he wants children and he says that he does, but she says what would happen if she just woke up with a huge pregnant belly and didn't know how she got it? She shows him her journal that she's been writing to herself. She asks him to help her edit it so that all references to him are removed, so she won't remember him at all. He is heartbroken but he helps her do it, including when she said that their first time sleeping together "didn't last long".
Henry tries to go back to his normal life but keeps thinking about Lucy. He sees her with a tour group from the memory clinic at the aquarium but while she smiles at him, she clearly doesn't recognize him. He gets ready to set sail on his finally finished boat and Alexa and Ula and his children and Lucy's father and brother stop by to see him. Alexa and Lucy's brother hit it off, and Ula tries to show his children how to flip off the dock but belly-flops instead. Lucy's father says that she went to live at the clinic a few weeks ago where she teaches an art class, saying she didn't want to burden them anymore. He gives Henry a present and wishes him good luck. After they leave Henry opens the present - it's a Beach Boys CD.
Henry starts to sail out and shouts about why he'd give him something that reminds him of Lucy. He sings along to "Wouldn't It Be Nice" and sobs, but then he thinks that maybe Lucy's father was trying to send him a message, saying that Lucy had remembered him. He runs over to the clinic to see her and asks if she knows who he is, but she doesn't. He starts to leave in despair but she asks him to come with her. She takes him to her studio, which is covered with paintings and drawings of him. She says that she doesn't know him, but that she dreams about him every night. They kiss, and the scene fades out on them together.
Lucy wakes up in a strange room with shorter hair, wearing a kind of silk kimono. She looks around, clearly not understanding where she is. She blinks and sees a tape next to her that says "Good Morning, Lucy." She puts it on and watches the usual tape about her condition, and at the end is a scene of her marrying Henry. He's wearing a Hawaiian yarmulke and Ula is performing the ceremony. Alexa and Lucy's brother are in the audience watching the wedding, and are apparently together now. Ula asks Henry if he still wants to get married even though Lucy may someday let herself go and making love to her will be disgusting, and Ula's wife, a very large woman, flips him off from the audience. At the end of the tape there's a title card saying that it's very cold outside so she'll need to put on a coat before she goes out. Lucy goes to the window and sees that she's on Henry's boat, and that they're in icy waters off Alaska. She goes up to the deck in a coat and sees Henry, who asks her if she wants to meet her daughter. There's a little girl there who looks about three years old who Henry introduces as Nicole. He also points out that "Grandpa" is there with them on the ship, Lucy's father. Lucy, amazed, hugs her daughter and starts to cry with joy.
Over the ending credits we see bits of Lucy's journal, including a drawing that Henry tried to pick her up with early in the movie that showed fishermen and walruses and baby pictures of Nicole.