Owen Browning, portrayed by Adam DeVine, is a young bank manager eagerly preparing for his upcoming wedding to his fiancée, Parker McDermott. As the couple gets ready for the big day, Parker's estranged parents reach out, which has Owen thrilled to finally meet them. However, Parker is somewhat anxious, knowing her parents can be overbearing.
Owen's own parents, Neil and Margie Browning, add to the stress. In a phone call to break the good news about Parker's parents attending the wedding, Owen is bombarded with complaints, including offbeat concerns about a guest's nickel allergy, and their complete lack of understanding regarding Parker's career as a yoga instructor, jokingly confusing it with something far less reputable. Instead of celebrating the positive news, they criticize the McDermott family for their absence in Parker's life.
While at work, Owen faces another dilemma when he has to rescue an employee troubled by being trapped in the vault. This incident gives him an opportunity to boast about the state-of-the-art security system in place, though he is reminded by his colleagues that their rival bank is known for having the best vault security in the state. Additionally, Owen mentions the emergency escape latch all vaults possess.
During a dinner with his parents, discussions arise about the imminent arrival of Parker’s parents. Owen also attempts to tap into some family history by contacting the storage facility where Parker’s parents keep a locker. However, this mundane inquiry inadvertently catches the attention of crime boss Rehan Zakaryan, who learns about Owen's investigation into the McDermotts.
Entering the scene are Parker's parents, Billy McDermott and Lilly McDermott, who unexpectedly walk into their home while Parker is occupied with a yoga class. They quickly insist that Owen address them as Billy and Lilly. The couple shares that they met because of Owen’s persistent attendance at Parker's yoga sessions due to his hip problems, leading to Parker finally asking him out after a year and a half.
To bond with his in-laws, Owen takes a day off from work at their request, joining them in thrilling activities that include skydiving and getting tattoos. The adrenaline-loving McDermotts starkly contrast with Owen’s more laid-back personality, heightening the comedic tension.
Things take a turn when the notorious "Ghost Bandits," a pair of criminals dressed in full costumes, rob Owen's bank during his wedding week. Signs point to the possibility that these criminals may actually be connected to his soon-to-be in-laws. His prior discussions with Lilly about the bank’s security codes raise frantic suspicions in Owen's mind.
As FBI Special Agent Roger Oldham interrogates Owen with his in-laws present, Owen struggles to find his voice, overwhelmed by the revelation that the McDermotts might be involved. Despite Parker's initial skepticism towards Owen's theory, he begins piecing together a conspiracy that puts him in a moral quandary.
In a shocking twist, Owen overhears Rehan threatening Parker, demanding an exorbitant $5 million ransom stemming from a prior robbery orchestrated by the McDermotts. When Oldham stumbles across evidence that wrongfully implicates Owen, they devise a plan to record a confession from the McDermotts. However, chaos erupts when Rehan's henchmen take Parker hostage.
To save her, Owen reluctantly teams up with the McDermotts, who reveal Rehan had initially been their partner but turned rogue. They plot to rob a bank on their own terms, with Owen believing he can help them pull off the heist within just two days.
Their first target, Victory Union Bank, proves to be a disaster filled with comedic hiccups. Though they manage to steal cash from an armored car, Owen’s clumsiness leads to yet another bungle, chasing them into a graveyard as the police chase intensifies.
They redirect their focus on Atlas Reserve, where Owen cleverly ingratiates himself with Phoebe King, the manager, under the pretense of enhancing his bank's security. While he distracts her, the McDermotts create a diversion, and Owen uses the emergency escape hatch to make off with more cash.
At the final showdown, Owen surprisingly manages to outsmart Rehan, miraculously thwarting her plans as the McDermotts turn themselves in, helping Oldham tie up loose ends. However, they get a brief reprieve to join Owen and Parker’s wedding celebration.
As the credits roll, Owen finds a sneaky way to aid his in-laws by leaving a paperclip in the wedding cake—an ingenious tool to help them escape their handcuffs.
