We open on Sam (Darren Criss) at home getting ready for his high school graduation, while hearing about how proud his parents are of him, and the plans they have for his future. Sam got accepted to the college his parents chose for him: his parents’ alma matter, and a top tier Ivy League school. Still, something is missing. That evening, Sam arrives with his parents at his high school, and they run into the parents of Ethan, one of Sam’s old friends. Sam wonders where Ethan is, but Ethan’s parents tell him that Ethan is riding with his friends. Sam’s mom puts Sam’s Valedictorian sash over his shoulder and Ethan’s mom remarks how proud they must be. As they walk into the building for graduation, Sam sees Ethan (Josh Hutcherson) pulling up in a car, having a blast with his friends. Sam stands before his class as the Valedictorian and gives a speech about being proud of accomplishments and their impending future. Sam sits back down, wondering where his childhood went. Sam sits through graduation and watches as his friends all take the stage and accept their diplomas: Ethan, Howie (Joey Richter), Kaytlin (Zoe Kravitz), and Zoey (Britt Robertson). After graduation, Sam catches the other four outside and hears them talking about a party they’re going to. Zoey, however, won’t be going to the party because she has to go back to work, and she’s seems to really hate her job.

That evening, Sam tries to get his dad to loan him the keys to his car so he can go to the party, but Sam’s dad refuses. He tells Sam that he is expected to work with his father over the summer, starting tomorrow morning. Sam is furious that he now has to give up his summer as well and storms up to his bedroom. Sam finds himself in his bedroom staring at pictures on his wall of Ethan, Howie, Kaytlin, and several pictures of him and Zoey together. Finally, we see one of them kissing. Sam decides that it’s time for a change, and he sneaks out of his bedroom window. At the party, Sam finds his friends are having a great time. At the party, he finds out that Ethan, Zoey, and Kaytlin are all leaving the state to go to school, just like he is, and Howie is going to the state university 30 miles away, staying at home with his parents, and commuting. Sam realizes that they’re all about to be split up for good. In his conversations, Sam finds out that Zoey’s mother passed away from cancer in the middle of their senior year. All Zoey wanted was for Sam to be there for her, and he wasn’t.

The next morning, instead of working with his dad, Sam meets Howie for breakfast, where he apologizes for not hanging out enough. Howie says that’s OK, and quickly forgives him. Sam tells Howie that he has an idea for everyone, and he needs Howie’s help in convincing the group to hear him out.

Later, all five are at Howie’s house. Ethan and Zoey are apprehensive about Sam being there. Sam pitches his idea: each of them make a list of 20 things they want to do before the summer is over, and the five of them will spend all summer doing what Sam calls “100 Things To Do Before You Die, or Go To College.” Howie has already made his list, and guilts them all on board. They spend the afternoon each crafting their lists and posting them on the wall inside Howie’s garage, where Howie also sleeps. Once they’re posted, Sam sees something they can immediately knock off of Howie’s list. The gang then is shown at an area restaurant where Howie is trying to down a 2 pound burger so he can get his photograph on the wall. Sam, Ethan, Zoey, and Kaytlin are all cheering him on. When he takes his final bite, everyone cheers him on, and Sam says 99 things to go. Outside the restaurant, Ethan finally opens up to Sam how he feels like he lost his best friend, and he’s got a long way to go. Sam understands, and apologizes. Zoey is still avoiding Sam. That night, Sam goes home and faces another fight with his dad, and he tells him he’s not working this summer, that he worked hard enough getting a full ride scholarship, and getting into the school that his parents picked. He’s doing what he wants this summer. His dad still isn’t happy.

We cut to the five main characters walking through the mall together. Kaytlin is having reservations about checking something off her list, but everyone else Is there to support her. Kaytlin enters one of the stores, while everyone else waits for her, and strategizes how to complete the rest of their lists. Howie has placed going motorcycle riding with Ethan, whose Dad owns a motorcycle shop. Howie wants Ethan to get his dad to lend them motorcycles so they can go for a ride, but Ethan is hesitant. Kaytlin comes back out and reveals that the thing she just crossed off her bucket list was shoplifting. She stole a sock. She laughs as everyone makes fun of her for her choice of item to steal.

The rest of the day spent in the mall is checking off things on their bucket lists, in a montage, ie., Zoey’s is to kiss a random stranger (so she kisses an old man sitting on a bench, and then runs away). That evening, we are back in Howie’s bedroom, and they have a mini dry-erase board on the wall next to the lists. Kaytlin is writing the new number on the board: 89 Things. This is when she glances at Howie’s list and sees “have sex with a girl” on there. She smiles. Another day is spent down by a creek, where Ethan is about to check white water rafting off his list, but Kaytlin is going to check public nudity off of hers first. Kaytlin thinks that its just the group of them, but as soon as all of her clothes are off, their rafting guide comes up behind her. He just laughs it off. They all get into two different rafts with three people each. Ethan, Howie, and Kaytlin ride in one raft, while Sam, Zoey, and the guide ride in the other. Howie spends most of the ride talking about Motorcycles, while Zoey finally opens up to Sam about what she’s been going through since she lost her mom. They hit a rough patch in the rapids, but everyone comes out OK on the other side and they all had a blast. We cut to Howie’s room that night, with Kaytlin changing the number to 82.

On another day, Zoey has enlisted Sam for help with completing one of the challenges on her list. Take a dance class. Zoey has signed them both up for a ballroom dancing class, for which she needed a partner. Sam is glad he can help. While Sam and Zoey take the class, and get closer, Ethan and Howie go talk to Ethan’s dad about borrowing some motorcycles for a ride. Ethan’s dad tells Howie that it isn’t a simple task, and he’ll have to learn how to ride the bike first. He tells Howie to come back tomorrow and he’ll show him how to ride a bike. While all this is going on, Kaytlin is completing another task by getting a tattoo. We don’t see what it is… yet. We then cut to the next day, and Howie, Sam, and Ethan all show up to learn how to ride a motorcycle.

While the three boys are riding motorcycles, Kaytlin and Zoey are completing their own bucket lists. Zoey’s task is to quit her job at the supermarket, because she’s tired of terrible customers, and her managers failing to do anything about it. She marches in, and with the support of Kaytlin, she’s strong enough to quit. Kaytlin reminds her that she would have had to anyway at the end of the summer to go to college. Kaytlin’s bucket list involves an old foe from high school, who went on a power trip during their last production. Kaytlin and Zoey drive over to the kids house, but they see that he’s living in total poverty. Kaytlin sees her nemesis sitting on his front porch, trying to keep track of several younger kids, and she decides instead to get out and help him. Kaytlin and Zoey spend the rest of their day with him and his younger siblings.

The next morning, Sam wakes up to find his dad is fuming. He’s found out what Sam’s been doing in his spare time, and he’s decided to take away Sam’s possessions until Sam wises up and goes to work for him. There’s no more TV in his room, no computer, and no X-Box. Sam has been having a great time without all that stuff, so he shrugs it off and leaves his house. He goes over to Howie’s for the meetup and asks if he can crash there for a bit. Kaytlin and Zoey come over and inform Sam and Howie that Ethan won’t be joining them, as he has to travel upstate because his grandfather is about to die. Sam decides that they’ll travel up there too, and be there for Ethan. This decision sits well with Zoey, who gives him a big hug. While loading up the car for their trip, Sam tells Zoey that he and Ethan spent an entire summer as kids up at his grandfather’s house, and that it was the best summer of his life.

Up at the grandfather’s house, Ethan and his mom are sitting in the grandfather’s bedroom. He’s still awake, but he’s weak and doesn’t have much more time. Sam, Howie, Zoey, and Kaytlin enter the room. Ethan is glad to see them. Ethan says that his dad didn’t come, even though it’s his father, because they haven’t spoken in 10 years. Sam relays more of the story about the summer he spent up here with them. Ethan’s grandfather becomes lucid while hearing Sam’s story, and says he’s happy that Sam and Ethan stayed friends. He asks them what they’ve been up to, and he explains the list. Ethan’s grandfather says that he and his friends had a much shorter list before being drafted into Vietnam, and he still has things he would have liked to do. Sam asks him if there’s anything they can do for him, and his grandfather whispers something into Sam’s ear. Sam replies “I can do that.” Zoey prompts the non-family to leave, so they do, and let Ethan and his mom have a few final moments.

Ethan exits the house and finds the other four waiting for them. Ethan sees that Howie rode a bike up, while Sam, Kaytlin, and Zoey took a car. Ethan is furious that Howie would take the bike without permission, and accuses him of just using this as an excuse to get another check off his list. Ethan grabs his own bike and takes off. Howie chases after him on his bike. Sam, Kaytlin, and Zoey hop in the car and try and follow them. Ethan is picking up speed, and Howie is trying his best to keep up. Ethan is more experienced on a bike than Howie, and as he blasts around a corner, Howie has a hard time with it and ends up crashing and flying over the guard railing. Ethan hears the crash, slows down, and turns his bike around. The car also stops at the crash site. Sam, Zoey, and Kaytlin get out in a panic. Ethan pulls his bike off the road and runs back to the crash site too. All four of them are calling for Howie, who is down about 50 feet in a ravine. Finally, Howie responds.

Later, at the hospital, the other four are standing at Howie’s hospital bed. Howie has only suffered a broken right arm, broken left foot, and a few cuts and bruises, but other than that he’s fine. He tells them they all have to complete the list without him. Howie seems sad that he won’t get to complete everything on his personal list, and Kaytlin remembers seeing something on Howie’s list she can help him complete. Kaytlin tells Zoey, Ethan, and Sam to wait outside and keep watch on the door. Kaytlin tells Howie how she’s always liked him, and how she remembers how Howie was the only friend she had when her Dad left her when she was 7. Kaytlin shows Howie her tattoo, a little heart right below her waistline. In the hallway, Ethan’s dad shows up, furious about what happened, but grateful that Ethan’s OK. He asks to see Howie, but they tell him it’s not a good time. He’s “resting”. Sam tells Ethan’s dad what Ethan’s grandfather told him, which was that he’s sorry for whatever he had done 10 years ago. Ethan’s dad falls apart, emotionally, realizing the mistake he made not going up to see his dad pass. Ethan asks his dad what it was, and his dad replies that he can’t even remember. Ethan takes his dad off to a waiting area, so they can talk, leaving Zoey and Sam there. They start talking about the last time Zoey was in the hospital with her mom, and how hospitals always bring bad memories, when Sam’s dad shows up. Sam is afraid that his dad is going to be mad at him, but instead, he starts crying. Sam’s dad is just happy that he’s OK.

Later on, the kids meet in Howie’s bedroom, even though Howie isn’t there, to assess how many things are still on the list. 47 things. They’ve completed just over half the list. Sam notices that there’s something that him and Zoey have on both of their lists. Skinny dipping. They wait until nighttime, and jump the fence at the community pool. Sam, Zoey, Ethan, and Kaytlin all, one by one, take off their clothes and get into the pool for some skinny dipping. It’s a rush at first, and it’s the last thing that brings Zoey and Sam closer together. Sam kisses Zoey, while Ethan and Kaytlin cheer them on. Sam says this has been the best summer of his life. Ethan says that he wishes they were all going to the same school, but maybe they can do this again next summer. Zoey says she’s excited to be going to school, and that she’s wanted to be a doctor so she can help people like the people who took care of her mom. Kaytlin is going to school for theatre, and Ethan is going to school for physical therapy. Sam realizes that he still has no idea what he wants to do in college, just that he’s going to college. Ethan hears a police siren in the distance that appears to be getting closer. They all hop out of the pool and quickly grab their clothes. One by one, they help each other over the fence, with Sam being the last one on the other side. He’s not coming. Sam tells the other three he can buy them some time to get away. Ethan, Kaytlin, and Zoey run away, while Sam dives back into the pool, content with his choice as the cop car pulls up outside the pool.

Sam’s parents show up, angry about the situation. They tell him he just threw away his scholarship, and Sam tells them they never asked him what he wanted to do, they just told him what he was going to do. They wanted him to be a lawyer, but it’s not what he wants, and he needs to figure that out before he can go to school. He reminds them that somewhere there’s a college that will take him, because he has great SAT scores and he’s still the Valedictorian, and this one juvenile record stunt won’t matter in a year. His parents are confused, but they’re again glad that their son is safe and now out of jail. Sam returns to Howie’s house, where Howie has returned from the hospital and the others have already met. Sam tells them that he said he was swimming alone, and he just got a trespassing misdemeanor that will be a part of his juvenile record. They ask him about college, and he asks Zoey about her college. Zoey kisses Sam, realizing that he chooses her. Everyone in general seems to be happy. Howie asks about the remaining tasks on the list, and Sam says they’ve still got the rest of the summer. The film rolls to credits with footage of Sam, Ethan, Howie, Kaytlin, and Zoey doing more things off their lists.