Cleveland teenager Wren Desantis (Victoria Justice) narrates about how Halloween is a big deal for all those around her. She is more preoccupied with going to college in New York. She misses her father Pete and lives with her mom Joy (Chelsea Handler) and little brother Albert (Jackson Nicoll). Albert hasn't spoken for nearly a year after his father's passing but enjoys messing with his sister, such as pooping while she showers and cutting her shirts.
Wren goes downstairs and asks Joy if she filled out a loan application for her, but she hasn't. She's preoccupied with her young boyfriend Keevin (Josh Pence - and yes, that's with two E's).
Wren walks to school with Albert and her best friend April (Jane Levy). They're talking about costume ideas for a party - April wants to be a sexy kitty while Wren considers going as Ruth Bader Ginsberg. A nerdy kid named Roosevelt (Thomas Mann) comes by to talk to Wren. He says he's going to dress up as EO Wilson, and he and Wren make up a cheesy rap about it. April covers her face in embarrassment as Aaron Riley (Thomas McDonell), aka the hottest guy in school drives up and checks Wren out as she dances goofily. He invites her and April to his party, which she accepts, and April is thrilled, until Albert ties her shoes together and makes her trip.
Wren takes Albert costume-shopping. He takes a fake severed arm and Wren buys him a Spider-Man costume. April puts on her sexy kitty outfit, and Wren decides on going as Dorothy Gale. However, Joy informs Wren that she is going to a party with Keevin and Wren is stuck with Albert.
That night, Wren and April take Albert trick-or-treating, where he immediately causes trouble by taking a lot of candy and scaring kids. Wren takes him through a haunted house where she and April find Roosevelt in his EO Wilson costume, and his friend Peng (Osric Chau) dressed as Aaron Burr. With their backs turned; Albert gets lost. Wren scrambles to search for him, but he's already run off.
Albert goes to a convenience store in costume and gets the attention of the cashier, Fuzzy (Thomas Middleditch), who recognizes him from the arcade. He gives Albert a free slushie and a few packets of sugar, and he is on his way out. As he leaves, a trio of kids in shadow costumes (I believe that's what they're called) come in to buy toilet paper and eggs as part of a revenge scheme. This inspires something in Fuzzy. He goes outside and finds Albert sitting alone, and, despite the implications, asks him to accompany him in his own little quest to "avenge a broken heart". The kid silently agrees.
Not long after they leave, Wren and April go into the store and find Roosevelt and Peng there. Against April's wishes, Wren asks Roosevelt if he can drive them around town to find Albert. Roosevelt says he has strict rules with driving, so he has to ask for permission. He takes Peng and the girls to his house where his mothers (Ana Gasteyer and Kerri-Kenney Silver) are telling him to ask for permission in Greek. He fails and isn't allowed, but he takes the keys anyway and gets to take the Volvo out.
Fuzzy takes Albert to an apartment complex where he is going to confront his ex-girlfriend for going off with a douchey-sounding guy named Jorgen. They try to TP the place, but it fails. He climbs the ladder to the apartment window and tosses a roll in there, but it lands on a candle and catches fire. He tries to extinguish it, but he finds out that the ex, Lara (Abby Elliott) is in the next apartment, and the apartment he's in belongs to a Samoan couple. That couple pulls him in and starts to assault him. Meanwhile, his car starts to get towed, and Albert realizes he left his candy stash in there. He hops in the car as it's taken away, and as Fuzzy runs outside, he asks Lara for help.
Joy goes to Keevin's party thrown by his brother Brueder. Everybody is hanging around drinking and doing other sorts of vulgar activities that Joy realizes she's made a mistake.
Wren tells Roosevelt to drive to Captain Chicken, a fast-food restaurant, to find Albert since he loves that place. They happen to drive down a strip full of "cool" people, right as Peng puts on a cheesy love song that blasts on the stereo. To make matters worse, the car stalls in the middle of traffic. To make matters even MORE worse, Peng calls out two guys, dressed as a gladiator and Hulk, who are honking at them. They come to attack Peng and Roosevelt, but once the Hulk guy pounds the car with his Hulk fists, the car starts again and they drive off. They drive to the chicken restaurant, nearly hitting Albert as he walks by, but he is pulled away by a young woman. Wren asks the drive thru girl if she's seen Albert, but she hasn't. They drive into the path of the gladiator and Hulk guys, and Roosevelt backs up into the giant mechanical chicken, which falls on top of the car and appears to be humping the car. April snaps at the nerds and Wren for ruining the night. Peng steps out with his musket (part of his costume) to challenge the gladiator guy. He mockingly takes a drumstick and pretends to duel with him, but Peng fires the musket and makes the gladiator guy scream like a girl, causing the crowd to laugh at him. When they go back to the car, they discover April has left. Wren and the nerds go back to look for Albert.
Unbeknownst to them, he goes off with the girl who saved him. She is dressed as a Galaxy Scout (Riki Lindhome), a character from Albert's favorite comic. She takes him with her friends to another party. At this party, Albert starts to dance and have a good time, but a large douche with a mullet comes in and starts dancing with the Galaxy Scout. Albert recognizes him from Fuzzy's description as being Jorgen (Johnny Knoxville). He takes Albert's candy stash and starts dumpling it all over the place. Albert follows him.
Wren gets a call from April saying she's at Aaron's party and that she found Albert. She gets the nerds to drive off there, and as it turns out, he isn't there, but April lied to Wren to get her to come. Wren gets mad and walks out as Roosevelt follows her outside. Meanwhile, Peng gains attention after scaring off the gladiator guy.
We go back to Joy, who is having tea with Keevin's parents. She tearfully opens up to them about how hard it is to be a single mother with two kids, especially since Wren is close to going off to college. She decides she has to go back home to them.
Fuzzy and Lara come across the club party and find the Galaxy Scout with her friends. They lost sight of Albert, but as Jorgen drives up to holler at Lara, Fuzzy sees Albert hiding in the back of his car.
Back at Aaron's, Roosevelt almost confesses his love for Wren, but April comes out and apologizes to Wren for being a bad friend earlier. She brings her back in as Aaron, dressed as Jack Sparrow, starts to sing a song for Wren. Thinking she will choose Aaron over him, a heartbroken Roosevelt leaves. Wren realizes she prefers Roosevelt before she can kiss Aaron, and she leaves him. Aaron also appears heartbroken until he asks the other girls in the room if they want to kiss him, to which they all raise their hands (as well as one guy). Meanwhile, Peng finds April by herself and recalls a deal they made in the car over allowing him to grab her boob. She lets him do so but then slaps him.
Fuzzy catches up with Albert, and together, they prank Jorgen by getting a bag of dog poop and sticking some firecrackers in there. They succeed, but Albert gets caught and taken inside as Fuzzy is helpless to save him.
Wren gets a text from her mom saying she's about to be home. She then gets a call from Jorgen saying he's got Albert, but he is demanding a ransom. He gives her the address, and without any other way of getting there, she runs down there. She finds that Albert is locked in a room trying to get out. She has no money, but when she notices that Jorgen is a Beastie Boys fan, she tries to give him a jacket she's been wearing the whole time that belonged to her father, but originally belonged to Mike D after he left it in a recording studio (her dad was among the guys working on the License To Ill album). Jorgen takes the jacket but still wants money. At that moment, Fuzzy tosses more firecrackers into the home, allowing for a distraction, so Wren can get Albert. Before they leave, Albert socks Jorgen in the nuts and they run out. The police start to come, so Fuzzy creates another diversion by running away naked.
At Roosevelt's home, he laments to his mothers that he wrecked the car and failed with Wren. One of the moms tells him that they are not upset about the car but that he shouldn't give up on Wren. He gets a voicemail from her, and she thanks him for his help that night and appreciates him for being there. His moms encourage him to go back after her.
Wren and Albert go to a cemetery and leave some flowers in Albert's pumpkin candy bucket on their father's grave. Albert finally speaks and says thank you to Wren. As they leave, they find Joy waiting for them.
They get home at the crack of dawn and find Roosevelt standing outside, thinking Wren is still in trouble. Joy tackles him to the ground, but Wren convinces her to let him go after he declares his love for her. The two of them finally kiss.
Around the same time, April wakes up at Aaron's house with Peng. They apparently hooked up the night before, and they start to make out again.
Fuzzy is back at the convenience store where the Galaxy Scout girl (name revealed to be Denise) sees he is reading a Galaxy Scout comic. He gives it to her for free after lamenting that he and Lara were not meant to be, and the two of them make an arrangement to hang out.
Joy finally fills out the application for Wren's college loans. As this happens, Albert uploads a video to Wren's Facebook page. April gets a notification of this and calls Wren. It turns out to be an autotuned video of the dorky rap she and Roosevelt did at the beginning. Wren sees this and screams.
Before the credits roll, Albert addresses the audience and tells how he's been prank-calling his mom. She eventually figures out it's him.
You can send in your spoiler to other movies by going here.