The film starts with Wade Walker (Craig Robinson) in a kindergarten classroom singing a song called "Speak It (Don't Leak It!)," in which he tells the kids to better express themselves rather than urinate their pants. He later goes home to his girlfriend Grace Peeples (Kerry Washington). Grace is preparing to go to her family's home in the Hamptons for Moby Dick Day, a traditional event that her father likes to attend. She plans on going alone, but Wade insists that she let him join her and for her to "share the chocolate Kennedys". She declines and says she'll be back soon enough. When she's not looking, Wade sadly pulls out an engagement ring.
He goes to visit his brother Chris (Malcolm Barrett), who works at a doll repair facility. He gets kicked in the shins by a girl who demands that he fix her doll. Wade complains to Chris about Grace's father and her not wanting them to meet, and we learn that her dad is a federal judge, so the bar is set high for Wade. Regardless, Chris convinces him to go out anyway.
The next day, Wade travels to Sag Harbor to the Peeples' large lake home. Almost immediately, Wade gets chased by the Peeples' dog, then getting pounced on by the dog and having his wallet fall out of his pocket and get taken away by the dog. He meets Grace's parents, Virgil (David Alan Grier) and Daphne (S. Epatha Merkerson) and introduces himself, but they have no idea who he is. Grace comes out calling "Peanuts!" (their safety word) and is followed by her sister Gloria (Kali Hawk) and Gloria's friend Meg (Kimrie Lewis-Davis). Grace awkwardly informs the family that Wade is her boyfriend. Virgil tells him that he will stay in the guest house and calls his youngest son Simon (Tyler James Williams) to help Wade with his bags.
Simon takes a liking to Wade when he refers to him as "Si". Wade notices he's wearing an expensive watch and makes Simon uncomfortable when he points it out. Wade then tells Grace he's upset that she didn't tell her family about him, but she just tells him to abide by a few rules to get on Virgil's good side. In the living room, the parents try to get to know Wade, but Virgil is unimpressed by Wade's wanting to be a child psychologist. It gets more awkward when Simon brings out a bottle of champagne that Wade wanted to give to Daphne as a gift. She gladly accepts it, despite the fact that she's in AA.
The family goes out to get lobster for dinner, and Wade makes a comment that it looked rainy outside. The Peeples glare at him since Virgil thinks that anybody mentioning rain will automatically summon rain. They all ride bikes to the market, where Wade notices some activity between Gloria and Meg. They walk away just as a guy named Skip (Jerome Preston Bates) comes around and says hi to Grace. Skip tells Wade that he used to date Grace, and Wade is put off by the fact that the guy is significantly older. Another guy passes, and Skip says he took Grace from her. Wade walks away and goes down an aisle where he sees Virgil talking to a woman, Mayor Hodge (Ana Gasteyer). They make plans of some sort that sound sexual in nature. When Wade goes up to pay, he doesn't have money and Virgil covers for him, albeit begrudgingly. The family then leaves as Virgil cries "Run, chickens, run!", which means he wants to race. Grace tells Wade to race Virgil so he can beat him home, and then it starts pouring rain. When the family gets home, the groceries are messed up.
As the family sets up for dinner, Wade chats with Daphne, who notices him checking out family photos. Daphne was apparently part of a musical group that sang a popular break-up tune, and Virgil played the saxophone in his youth. He also sees a picture of Grace, and Daphne points out that Grace had a boob job because she felt competitive with Gloria. Wade admits he did not know any of that.
During dinner, Wade proposes an exercise where the Peeples say something they love about anybody in the room. Things get odd as Meg starts implying something intimate with Gloria, and then Simon gets mad when he feels that Virgil doesn't understand his "swag" like Wade does.
Wade goes out that evening to get fresh air. He goes to a bar called the Lusty Sea Hag believing Virgil is playing there, but he isn't. He rides his bike around a private beach to lay in the sand, but is spotted by Mayor Hodge, who is nude. She tells him to leave but then comments he would be a good partner for a three-legged race. Before Wade leaves, he notices Virgil there, stripping down to nothing, and Wade catches an unfortunate glimpse at Virgil's privates. He rides away trying to get it out of his head.
When he gets home, he finds Gloria and Meg playing pool. They admit that they are in a lesbian relationship, and they ask Wade, believing him to be a professional therapist, to determine that for Gloria. Later, he goes to the guest house to find Grace wearing her old private school uniform. Wade admits he was surprised to find out about Grace's implants, but they eventually start getting into some roleplaying, which Virgil happens to see from the window.
The next morning, the family is preparing to go to Virgil's parents home. He implies that he knows about the roleplaying from the previous night. Wade goes upstairs to get Simon, only to find him performing a rap music video. Wade also spots a lot of money and jewelry near Simon's bed. Then he goes into Virgil and Daphne's room and finds a headpiece of Daphne's from the 70's. He tries it on and sings her group's song and is caught by Virgil. Wade then gets a phone call and rushes outside.
It turns out Chris has made a trip to help Wade out. He instantly makes a good impression by fooling Virgil into thinking he is part of his old fraternity and that he is a professional doctor. He also finds himself attracted to Gloria, unaware that she's a lesbian.
Everybody goes to the home of Grandpa Peeples (Melvin Van Peebles) and Nana Peebles (Diahann Carroll). Grandpa already starts asking Wade if he has marriage plans for Grace, which he sees as an opportunity to propose, but is interrupted when lunch is announced. During the lunch, Wade starts playing a guitar and influences Daphne to sing her group's song, and then gets everybody to dance. Nana points out to Virgil that she hasn't seen Daphne move like that in ages.
That evening, Daphne cries because her earrings are missing. Virgil immediately accuses Wade. Wade tries to defend himself by implying someone else took them, but he can't bring himself to say he's thinking Simon took them. He later goes to the Lusty Sea Hag with Chris, where they find Simon wearing his mother's earrings and trying to pick a girl up. They follow him to the bathroom and interrogate him, and in the process, Wade learns that Grace was in jail for three days before Virgil bailed her out. Simon sees that it's them, and Wade tells him that he's a smart kid and can pick girls up by being himself.
Wade goes to the sweat lodge where Virgil is meeting with other people. He decides to finally tell him straight up that he plans on proposing to Grace. Virgil tells him to "walk through the flame into manhood" by walking across flaming hot coals. At the same time, Gloria tries to get Chris to have sex with her, but she is not feeling it and asks him if Meg can join. He thinks he's getting a threesome, but he's not. Wade, meanwhile, starts experiencing hot flashes and knocks over the chief with the shovel of coals, and then burns the tent down.
Wade wakes up the next morning with a note on his head from Grace, who tells him to meet her in town for Moby Dick Day. When he gets there, she notices he doesn't look good, and she gives him a drink. He puts the lid back on and sees a note that says "For Daphne only" with a mushroom drawn on it. Virgil goes up on a fake boat acting as Captain Ahab and reading from Moby Dick just as Wade starts tripping out. He thinks Virgil is mocking him and being condescending, so he flips out and runs up to Virgil. He grabs the harpoon and runs at him, but Virgil trips him and causes him to fall over the mast and knock himself unconscious. Chris also passes out when he sees blood on Wade's head.
The brothers wake up in the Peeples' living room. Grace tells Wade he was tripping on shrooms, and Virgil accuses him of being a junkie. Finally having had enough, Wade then tells the family that he saw Virgil at the private beach, but Virgil looks away and refuses to acknowledge this. Wade starts leaving and asks Grace if she's coming, but she doesn't. Chris leaves with him. Virgil feels content about sending Wade out, but the family confronts him, forcing him to admit he was indeed at the nude beach. The rest of the family comes out with their own secrets - Daphne put shrooms in the drink for herself, Simon stole his mother's earrings, and Gloria comes out to the family. The dog then brings in Wade's wallet, proving that he wasn't scamming Virgil for some money. Simon also pulls out the engagement ring that he found in Virgil's pants pocket. Grace feels awful when she sees a message written in the ring and realizes Wade was going to propose.
Grace returns to the city to her and Wade's place, but he isn't home. She looks at his planner and sees he is at a kids museum. She finds him setting up for a performance and apologizes for not being ready to introduce him to her father. They reconcile on the grounds that they keep no secrets from each other. Wade finally proposes to Grace, and she says yes. That's when Chris and the rest of the Peeples come out. Virgil finally shows humility and accepts Wade as part of the family.
The film concludes with Wade and the Peeples performing "Speak It (Don't Leak It!)" for the kids at the museum, and then later going back to their home to take a family picture with Wade joining them.
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