NOTE: This spoiler was submitted by Caboose
The opening credits roll by as we tour the summer Rhode Island house belonging to the Bishop family. The family consisting of the dysfunctional attorney parents, Walt (Bill Murray) and Laura (Frances McDormand), pre-teen daughter Suzy (Kara Hayward), and their three younger sons live in a red two-story house with a lighthouse overlooking the water. Their area is known as “Summer’s End.” The sons sit around all day listening to “The Young Person's Guide to the Orchestra” while Suzy occasionally hangs out on the lighthouse watching people with her binoculars. As the credits end, a narrator (Bob Balaban) wearing a red jacket and green beanie introduces the small island where the story takes place and the main community of New Penzance Island. He also tells us the year is 1965, and that the story takes place a few days before a huge storm.
We then cut to Camp Ivanhoe, a camp for boy scouts known as the Khaki Scouts. Scout Master Randy Ward (Edward Norton) wakes up and inspects all of the scouts to make sure they’re each doing their morning chores and building a fort (actually a treehouse in a tall/incredibly-unsafe tree). As they sit down for breakfast, Ward realizes one of the scouts is missing. He checks the tent belonging to Sam Shakusky (Jared Gilman) and finds he snuck out via a hole in his tent. After Ward finds Sam has written a formal “letter of resignation” from the Khaki Scouts, Ward goes to the island’s police station to report Sam’s disappearance. The station is a small, two room pier house which also acts at living quarters for Captain Sharp (Bruce Willis), who also appears to the be the only cop around. Via a radio, the two alert Sam’s parents, but are shocked when the father apparently tells them that they, “can no longer take the boy back.” They are Sam’s foster parents his real parents passed away some time ago. This shocks Ward in particular, as for some reason it doesn’t mention this on Sam’s scout registrar.
Disregarding the foster parents’ lack of concern, Sharp still issues out a search for the boy. After checking every end of New Penzance, Sharp finds his way to Summer’s End, where Walt doubts a boy could even hike this far. Suzy spies from the lighthouse she watches her mother meet with Sharp at a nearby landmark and suspiciously share a cigarette.
As it turns out, Sam is trekking through the woods in his scout outfit and a large pack of camping supplies. After following a trail and canoeing down a river, he comes across a wheat field near the Bishop house -- where Suzy is waiting for him. She holds a couple suitcases and a large bag with her cat in it. Sam asks if she was followed; she says no. The two smile at each other.
Cut to the summer before. The local church puts on a performance of Noye’s Fludde (Noah’s Flood), and Suzy plays a raven in the climactic scene on the ark. Sam watches the play with Khaki Scout troop he sneaks away and enters the girls’ dressing room. He asks Suzy what kind of bird she is, despite the other girls’ interruptions. Sam is brave and very talkative with Suzy, which impresses her. As Sam is chased away by an adult, Suzy asks Sam to write to her at Summer’s End.
Cut back to the present, where the two kids run away together. They adventure into the woods, with Sam constantly sharing his camping knowledge and Suzy willing to follow his lead. They take inventory on Suzy’s stuff, which includes a record player, a pair of Lefty scissors, and a suitcase full of her favorite girl hero/bizarre sci-fi books (which she reads to Sam every night throughout the movie). Sam notices the books are from library, and asks Suzy if she likes to steal. When Suzy says she doesn’t mind, we can tell Suzy has a few problems at home. This is evident when she pulls out a pamphlet she saw her parents hiding it reads something like “Conflicts and Solutions with the Troubled Youth.” Upon seeing this, Sam laughs. An offended Suzy coldly tells him “this is why you don’t make friends.” Realizing his mistake, he apologizes to Suzy, who accepts.
Back at Summer’s End, a panicked Laura runs around the house (shouting through a bullhorn) looking for Suzy. One of Suzy’s brothers gave Laura a note that Suzy wrote asking to borrow his record player for 10 days, thus cluing the family in on her disappearance. Walt is less caring, but then notices Sharp waiting outside in his car. When he’s noticed, Sharp claims he’s still looking for Sam. Laura connects both of the kid’s disappearances when she shows Sharp a box full of letters written between Sam and Suzy. The letters show a huge relationship developing between the two the two vent to each other about their misunderstood lives (Sam always being picked on/Suzy’s troubled family and her violent temper), and eventually plot to run away together. Also inside the box are watercolor paintings of half naked people that Sam apparently paints. Laura sends the two men out to look for the kids; during this time, Walt shares his suspicions that Sharp has been with his wife.
Slowly losing his confidence after losing Sam, Ward also rounds up the scouts in an effort to find the boy. Led by motorbike-riding tough kid Redford (Lucas Hedges), the scouts interpret the search as a “hunt,” and equip themselves with different weapons. After finding the sight of their first camp, the scouts eventually track Suzy and Sam down. Sam tries reasoning that they should let him go since they don’t want him in their troop anyhow -- Redford agrees, but also says they’re supposed to turn him over to the adults. The confrontation gets heated when Suzy is involved when the scouts try to grab him, her temper flares and she stabs Redford with the Lefty scissors, puncturing his lung. One scout panics and shoots an arrow with his bow, accidentally killing the troop dog, Snoopy.
Upon learning about Redford’s injury, Walt grows furious and believes Sharp and Walt are clueless about what they’re doing. They inform Walt that Suzy was the one who stabbed Redford, infuriating him more. The fighting is interrupted by the Narrator, who claims to be Sam’s teacher (and also an expert of the island’s geography) and has an idea to where the two are heading to next.
Sam and Suzy continue on their camping trail until they come across a beach in the middle of a cove. Believing it to be an ideal spot, they set up camp here, and Suzy convinces Sam to swim with her although Sam mentioned earlier he’s not a good swimmer, he trusts Suzy and goes in the water. Later, as their clothes dry, Sam paints a portrait of a half-naked Suzy she admits that the beach needs a new name other than “Mile Marker 28.” They dance to Suzy’s records and eventually kiss for the first time. Their innocent love is capped off by them discovering French kissing and Suzy letting Sam feel her chest.
The next morning, the two open up their tent to find everyone has found them Suzy’s parents, Sharp, the scouts--everyone. They take them both on a boat back home, where Walt shares with his Suzy his disappointment and that she will never see Sam again. Ward is sympathetic to Sam, but sets him up to temporarily stay at the police pier station with Sharp until they know what to do with him now that his foster parents officially disowned him. Eventually they get a radio call from Social Services (Tilda Swinton), who has reviewed Sam’s case file and decides he’s too troublesome for another set of foster parents. She informs them that she’s flying out there to take Sam and bring him into a “juvenile refuge” home, which breaks Sharp and Ward’s hearts.
At the Bishop home, a despondent and drunk Walt goes out back to chop a tree down. As Laura bathes Suzy, Suzy claims she hates her mother then admits to knowing about Laura’s relations with Sharp. Despite Laura’s insistences that things will be better, Suzy remains miserable.
The Khaki Scout troops (minus the still-injured Redford) meet up in their ridiculously-tall tree house to discuss Sam’s situation. They genuinely feel for the guy considering he’s never done anything to deserve being picked on and that he’s “gotten to third base” and decide to help him escape. After helping Suzy get out of her house, they lower a rope down the police station’s chimney and pull Sam out.
The next morning, Ward wakes up to find his entire troop now missing. Once again panicked, he sends a Morse code message to the Khaki Scout headquarters where Scout Commander Pierce (Harvey Keitel) is appalled at Ward’s foolishness. Nearby, the scouts help Sam and Suzy sneak into the scout headquarters in an effort to get help from Cousin Ben (Jason Schwartzman), an eccentric counselor who helps the kids out with bizarre favors. Since Cousin Ben claims to be a licensed priest, the group pays him $76 (in nickels) to get the two lovebirds married and to sail them to a different part of the island. Ben marries them in a makeshift chapel (complete with a paper mache cross), and they prepare to leave the island in a sailboat however, Sam must run back to the chapel because Suzy left her binoculars. He runs back to find they have been taken by Redford, who’s been staying at the headquarters’ infirmary. Sam tries reasoning with him, asking Redford if there’s an actual reason as to why he dislikes Sam. When there’s no negotiating with Redford, Sam has no choice but to attack, hitting Redford where Suzy stabbed him. Redford alerts the rest of the scouts, and they engage in an epic chase for Sam. They lead him to a lightning field, where Sam is inexplicably struck by lightning. The chasing scouts scatter while Suzy and Sam’s troop run to his aid Sam simply says “I’m okay,” brushes himself off, and they flee.
The storm we heard about at the beginning begins to fall down on the islands. A dam breaks somewhere in the woods, leading the troops to call out a flash flood warning. As the rain pours, Ward eventually runs all the way to the troop headquarters, where a furious Commander Pierce strips him of his scout leadership duties. Pierce retreats back to his bunk right as the flash flood runs through. After the flood puts Pierce’s bunk in a dangerous spot, and somehow sets off fireworks in his tent, Ward acts quickly and jumps over the water to save Pierce’s life.
As the storm gets worse, most of the townspeople hole up in the church. Laura and Walt, who last heard their daughter was at the scouts' headquarters, are angry when Ward and Pierce show up at the church empty handed. Social Services arrives and demands Sam to be placed in her custody (especially after finding out he’s been struck by lightning), but Sharp and Ward are hesitant because of the “juvenile refuge” talk. It is then that Sharp notices that kids wearing bird costumes are watching them from the church’s second story one of them has binoculars. When Sharp gets distracted, Suzy and Sam flee into the storm outside and hide up on the roof. As Sharp goes after them, they climb the steeple up to its highest point. Realizing that their only option (other than surrendering) is to take their chances on jumping into a shallow stream of water, Sam shares his feelings to Suzy one last time. Before they jump, Sharp stops them and tells Sam he has offered to adopt him as he was climbing up the roof, Sharp communicated via radio with Social Services and attorneys Laura and Walt in an effort to make a legally binding arrangement. As Sam is relieved, lightning strikes the steeple. It is destroyed, and the final shot shows Suzy and Sam hanging onto Sharp’s arm for dear life as he dangles from the roof. He tells them not to let go, they stare at him with dry looks and never scream once.
Some time passes, and we see Suzy back in her house in summer’s end, reading to herself as her brothers play “The Young Person's Guide to the Orchestra” records. Sam is also in the room, painting a piture. When the kids are called down for dinner, Sam quickly flees out the window but not before saying goodbye and “I love you” to Suzy. He gets picked up by Sharp in his squad car, confirming that Sam now has a home on the island. As Suzy heads downstairs, we pan to the picture Sam was drawing….it is of the beach he and Suzy found and kissed at. The name they gave the beach Moonrise Kingdom is spelled out in stones on the sand.