The film opens with a Facetime conversation between Laird Mayhew (James Franco), a 32-year-old man, and his 22-year-old college girlfriend, Stephanie Fleming (Zoey Deutch). Excitedly, she invites him over for a "Netflix and chill" session, causing Laird to eagerly riff off various Netflix shows while inadvertently directing the camera towards his groin.
Meanwhile, in Grand Rapids, Michigan, Stephanie's younger brother, Scotty (Griffin Gluck), is busy preparing a slideshow at an Applebee's to celebrate their father, Ned (Bryan Cranston), on his 55th birthday. Their mother, Barb (Megan Mullally), and several of Ned's coworkers are present. In a hilarious mishap, Scotty manages to connect a live webcam feed to Stephanie right as Laird barges into her room, pants down, exposing himself to everyone. In a panic, Scotty tries to shut it down, but he ends up freezing the feed, after which Ned grabs the laptop and smashes it just as the restaurant employees begin singing "Happy Birthday."
Ned, who struggles as the CEO of a debt-riddled printing company, discusses the embarrassing incident with his coworker, Lou Dunne (Cedric The Entertainer). During their conversation, Ned learns that Stephanie has referenced Laird for the first time, wanting her family to meet her boyfriend who resides in California.
When Ned's family visits California just before Christmas, they meet a very unconventional Laird at his startlingly large home. He welcomes them exuberantly as "the motherfucking Flemings!" and introduces his assistant, Gustav (Keegan-Michael Key), who attempts to keep Laird grounded amidst the chaos. Laird proudly showcases his home adorned with oddities, including a moose tank containing urine and a bowling alley mural depicting Ned in an immodest pose.
Amidst the explosive behaviors and eccentricity, Ned expresses concern about Laird's antics during dinner, where Laird shares explicit stories about his intimacy with Stephanie. When she shoos him away, Laird vows to improve his conduct. A comedic series of events ensues when Laird introduces Ned and Barb to his high-tech voice assistant, Justine (Kaley Cuoco), aiming to pamper his guests but only causing more chaos.
One morning, an embarrassing bathroom incident occurs when Laird's "paper-free" rule leaves Ned in a predicament involving an automated toilet. Meanwhile, Laird attempts to seek Ned's approval to propose to Stephanie in a comical outdoors setting but is met with a swift rejection, leading him to silently strategize to win over his future father-in-law.
Later, as family dynamics unfold, Ned secretly investigates Laird for dirt to use against him, which results in unexpected complications, including a failed computer hack that leaves both men flustered. Then, amidst all the chaos, Laird throws a vibrant Christmas Eve party, inviting business associates which causes more friction as Ned can't help but disclose Laird's financial troubles.
In an unpredictable turn of events, Laird shockingly buys Ned's failing company as a gesture to alleviate his debts, leading to a physical confrontation that culminates in a hilariously messy accident involving the moose tank—a situation only made worse by Steph and Barb's displeasure. The Flemings leave in a huff, returning to Michigan amid the tumult.
As Christmas approaches, Laird surprises the family by flying in with a helicopter, ready to mend fences but facing a cold reception from both Stephanie and Ned. After many misunderstandings and humorous miscommunications regarding proposals and doves, Laird ultimately receives a bittersweet response from Stephanie who isn't ready for marriage yet wishes to continue their relationship.
In a fitting conclusion, Ned and Scotty team up with Laird on a new business venture stemming from their shared experiences, while the holiday celebrations proceed with a festive dance, solidifying Laird's place in the family—now affectionately dubbed "son" by Ned.
