NOTE: This spoiler was submitted by Jeremy

The film opens at a middle school science fair. Wednesday Addams (Chloe Grace Moretz) is set to present her experiment, but is dismayed when her family – Gomez (Oscar Isaac), Morticia (Charlize Theron), and Pugsley (Javon Walton) – show up. She proceeds with the presentation, where she uses a squid’s DNA on Uncle Fester (Nick Kroll) to show how humans can be improved. The experiment is a success, but when Wednesday goes up to accept what she thinks will be a first place prize, she finds that everyone got a trophy for their efforts, meaning she can’t prove she is the best. Her efforts are noticed by scientist Cyrus Strange (Bill Hader), who appears through a holographic projection to let her know he thinks her work is brilliant. Meanwhile, Pugsley attempts to impress the girls by tweaking another kid’s volcano project, but it ends up causing a huge disaster in the gym that sends everyone running.

Back at the Addams home, Wednesday and Pugsley decline to show up for dinner. Fester goes up to Pugsley’s room to try and help him find a way to woo the ladies better than his attempt at the science fair. Wednesday sends her parents a very specific note for why she isn’t coming to dinner. Gomez worries that the kids are drifting apart from him, so he and Morticia decide to take them on a family vacation.

Gomez brings out a hideous road vehicle and gets Thing, Fester, the kids, and Lurch (Conrad Vernon) to join him and Morticia on the road while Grandmama (Bette Midler) stays behind to take care of the house. Before they hit the road, a lawyer named Mr. Mustela (Wallace Shawn) approaches Gomez and Morticia with the implication that Wednesday was switched as a baby at the hospital, meaning she may not really be an Addams, but the two ignore him and think it’s just Wednesday trying to get out of going on the trip, but she says that she doesn’t know who that man is. Once the family is gone, Grandmama throws a huge party. On the road, Mustela and his hulking henchman Pongo (Ted Evans) pursue the Addams family.

The family is initially set on going to Salem, but Fester ends up making a detour to Niagara Falls because he is suddenly obsessed with water due to him mutating because of Wednesday’s experiment with the squid. Pugsley tries to make another attempt with girls per Fester’s advice, but his cheesy line backfires. Wednesday gets a voodoo doll of him and uses Pugsley to perform some dance moves, until she just tosses the doll over the Falls to torment her brother. When Gomez and Morticia attempt to bond with Wednesday, she snubs them. They then spot Mustela and Pongo looking for them, and Fester ends up knocking Mustela into the water before recovering Pugsley.

The family then stops in Sleepy Hollow where they set up camp. While gathered around the fire, Gomez and Morticia bring up Mustela and his claims about Wednesday, so Fester mentions a story from the night Wednesday was born where he went into the delivery room to see her, but all the other babies were crying. So he employed an Addams family tradition of putting babies to sleep…by taking them out of their beds and juggling them all over the place, potentially mixing up many babies in the process. This only worsens Gomez and Morticia’s fears that Wednesday was switched thanks to Fester. Wednesday overhears the discussion and muses to Lurch about where she might really come from.

Gomez brings everyone to Miami in an attempt to get in touch with Cousin Itt (Snoop Dogg) so he can help with their current dilemma. Itt joins them on the trip as they pass through San Antonio where he talks (kind of) to Wednesday about his own rebellious phase in his youth, but he essentially says he owned up to who he really is. When Grandmama calls him to help with the house party since she let it get out of hand, Itt must bail. Mustela and Pongo almost catch up with them, but Lurch knocks them away and causes them to steer into a giant pile of cow poo.

To hide from Mustela and Pongo, the Addams family goes to a motel where they put a VERY displeased Wednesday into a girls beauty pageant. She scares one girl with her mind reading powers and then doesn’t participate in the actual show, instead dumping buckets of red paint on them like “Carrie”. Mustela is almost fooled because of Wednseday’s disguise, but when he spots her parents, Gomez draws attention to him by making the other parents think he is a top talent agent, causing them all to pile on him while they get away. As this happens, Lurch and Pongo appear to make eye contact.

The family stops at the Grand Canyon where Itt flies off from them, and Morticia gives Wednesday a necklace containing the blood of the Addams family members. Pugsley blows up the canyon, drawing more unwanted attention. Meanwhile, Fester starts to mutate further into a squid-man. Wednesday goes off by herself where Mustela attempts to get her again, but she gets the drop on him and traps him. His phone rings, and she sees that he was employed by Cyrus Strange, who suggests to Wednesday that he is her true father and that he is inviting her to stay with him in Sausalito where she can hone in her potential in science. Wednesday runs a DNA test using Gomez’s hair, which seemingly proves that she most certainly is not his daughter.

Wednesday leaves the family while they sleep, but Lurch catches up with her to keep her safe. The rest of her family learns where she is headed and go after her. Wednesday and Lurch stop at a biker bar to ask for help in getting to Sausalito, which they do after Lurch shows off his piano and singing skills by performing “I Will Survive”. The bikers then escort the two to Sausalito.

Wednesday arrives at Cyrus’s home and meets his “wife” Ingrid, a bird-like humanoid being, and their “daughter”, Ophelia (Cherami Leigh). Cyrus brings her to his lab where he shows her a formula he developed much like Wednesday’s own that she used on Fester regarding human-animal hybrids. The rest of the Addams clan shows up, but Wednesday seems fully set on staying with Cyrus and no longer accepting them as her family. While Gomez and Morticia are sad, Pugsley tries to bond with Ophelia since they seem to be mutually attracted. However, Ophelia morphs into a pig, as that is what she originally was. When Pugsley brings this revelation to his parents, Cyrus reveals the truth and that he was just using Wednesday since her formula works better than his own. He then knocks out Gomez, Morticia, Pugsley, and Thing.

Cyrus traps the family in tubes where he plans to mutate them with his formula. He shows them to Wednesday so that she may remove any traits of theirs that she doesn’t like, but she doesn’t like seeing them trapped this way. She turns on Cyrus, but when he tries to have Pongo go after her and Lurch, it is then revealed that Lurch and Pongo knew each other and were really good friends at the asylum they were locked up at before Lurch was found by Gomez and Morticia. Pongo warned Lurch with a look that Wednesday was in danger. Together, the two brutes free the Addams family and knock Cyrus into a tube where he is doused with his potion. It turns him into a gigantic animal hybrid monster. When he goes after the family, Fester comes out as a giant squid monster, and the two fight until they both tumble out the window. Cyrus falls to his death while Fester pulls himself up with his tentacle, but he is now weakened. Wednesday uses the blood in the necklace that Morticia gave her, and Fester turns back to normal and is revived. Wednesday decides she is proud to be an Addams and reunites with her family.

The family returns home, with Ophelia joining them as a regular human girl, where Itt has helped Grandmama turn the party around. While Wednesday knows Cyrus fabricated the DNA test results, she wonders how her test came out so that she isn’t related to Gomez. He reveals his hair is a toupee, but that she is 100% his daughter. The family then goes on another vacation around the world.

Brought to you by

Fearing that their children are growing apart from them, Gomez and Morticia take them on a family road trip vacation. They are pursued by two men named Mustela and Pongo, hired by scientist Cyrus Strange to get to Wednesday. When it is suggested that Wednesday isn't really an Addams and was switched out at birth, she conducts a DNA test that seemingly proves this correct. She goes off to find Cyrus, thinking he can help her hone in her scientific capabilities.

The truth is that Cyrus just wants Wednesday to help him perfect a formula to perform experiments on animals and humans by mixing their DNA. When the Addams family tries to fight back, Cyrus imprisons them, but Wednesday realizes who her true family is and gets help from Lurch and another muscle man named Pongo to stop Cyrus and free the family. Cyrus turns into a weird hybrid monster, but Fester, who has mutated into a squid monster, fights him and sends Cyrus falling to his death. Wednesday turns Fester back to normal, and she learns that she really is an Addams after all, accepting her place in the family despite all their differences.