A straight-laced bank manager about to marry the love of his life. When his bank is held up by infamous Ghost Bandits during his wedding week, he believes his future in-laws who just arrived in town, are the infamous Out-Laws.

Owen Browning (Adam DeVine) is a young bank manager about to marry Parker McDermott (Nina Dobrev), whose estranged parents contact her to come to the wedding. He's excited he's finally going to meet them, as she's concerned they can be a bit much.

Owen's parents Neil (Richard Kind) and Margie (Julie Hagerty) are difficult. Owen calls to tell them the good news about Parker's parents attending the wedding. He first has to hear about an odd nickel allergy of a guest, then they show their ignorance of Parker's profession as a yoga instructor, believing it involves a stripper pole. Rather than being happy about the news that the other in-laws are coming, they criticize them for being absent in Parker's life.

At the bank, Owen has to free an employee who's been played upon by being locked in the vault. So, he shows and talks about how state-of-the-art their bank's security system is. They point out their rival bank's vault security is considered the best in the state. Owen also points out all vaults have an emergency escape latch.

Out at dinner with his parents, they talk about the soon appearance of Parker's parents. Meanwhile, Owen talks with the storage space facility where Parker's parents rent a locker as he's hoping to access photos of the Parkers for a wedding photo montage. His call inadvertently alerts the crime boss Rehan (Poorna Jagannathan) to their return, when the storage space manager tells Rehan about Owen inquiring about the McDermott's locker.

The following night, the McDermotts let themselves into their home while Parker is still out leading a yoga class and scare Owen. They insist he calls them Billy (Pierce Brosnan) and Lilly (Ellen Barkin). Owen and Parker tell Billy and Lilly that they met at Parker's yoga class due to Owen's hip issues. He went to her class for a year and a half before Parker finally asked him out. The next day, Owen takes off work to spend the day with the in-laws. They pick the agenda, so they go skydiving, get tattoos, and drink. The McDermotts are adventure freaks while Owen is a totally laid back, peace loving, normal guy.

The next day, an infamous full-costumed pair of criminals called the "Ghost Bandits" hold up the bank. As the robbery occurs during his wedding week, specific indicators such as the male's cologne, flashbacks to the bar, and what he told Lilly the previous day lead Owen to believe that the robbers might be his future in-laws. Owen had told Lilly about all the codes and the security measures to break into the vault. Unknown to Owen, Rehan had met Billy at the bar the previous night. Billy had told Owen that he knows nothing.

FBI special agent Roger Oldham (Michael Rooker) questions Owen as the bank manager with his in-laws behind him. Not able to say anything, Parker insists they leave once he breaks out in tears. Oldham has dedicated most of his career chasing the Ghost Bandits and he's convinced they are behind the robbery. Owen know that if the McDermotts robbed the bank, then he did too, as he told Lilly the codes.

Trying to enlist his parents' help in outing the McDermotts, Owen tells them his suspicions. They do ask direct inappropriate questions at dinner, but Billy and Lilly expertly redirect the conversation. Parker later asks Owen, but she thinks his theory is crazy.

The next day, Owen follows his in-laws to Rehan's and hears her threaten to kill Parker if they don't get her $5,000,000 more before the wedding. Billy had just paid Rehan $ 1 million, as that was the amount that Billy and Lilly stole from her. But Rehan wants the $ 5 million as penalties and interest. She gives them till end of the week to come up with the cash. Oldham stops Owen on the highway, finds planted evidence in the trunk (burner phones, voice modulators which makes it look like Owen robbed his own bank), and spills it on his in-laws. Oldham puts a wire on him, hoping to get the McDermotts to confess. Instead, Rehan shows up with her henchmen and takes Parker hostage as insurance. Disgusted, Owen joins forces with his in-laws. McDermotts say that Rehan was their partner. She would choose the banks. But she started losing it and they were afraid that they would find out about Parker. So, at the last heist, they took the money and ran. Owen says that he knows everything about banks and can help them rob $ 5 million in 2 days.

They first choose Victory Union Bank to rob as the bank manager is lazy. However, they lose most of the cash through a comedy of errors. They are able to steal the money from the armored car which was taking the cash from the bank, but the security kicks in and due to Owen's ineptitude, their getaway car is disabled. Owen eventually gets into the armored car, and rescues Billy and Lilly. But the cash was in their getaway car. They are pursued by the police, but Owen drives through a cemetery. The armored car smashes through the headstones, but the cop cars are not able to.

So, then they focus on Atlas Reserve. Owen goes in, asking it's manager Phoebe King (Lauren Lapkus) how he can better equip his bank. Phoebe is the best bank manager in the business and every inch of her bank is triple secured. Phoebe's arrogance kicks in, so she shows him all of the safeguards with him. Just as the safe open, the McDermotts create a diversion out front while Owen locks himself in and then uses the emergency escape latch to escape with the money.

At the ransom drop, Rehan is pleasantly surprised that Owen brought the money, but will kill them anyway. He miraculously guns them down as the McDermotts distract the cops so Owen can sneak back into the vault with the money.

As the McDermotts turn themselves in and help Oldham with his ex, he lets them go briefly to Owen and Parker's wedding reception. During the credits, Owen slips a paperclip into a piece of cake for his new in-laws to use to get free of their handcuffs.