Navy SEAL Lt. Shane Wolf (Vin Diesel) organizes his commandos to rescue a kidnapped American scientist, Howard Plummer (Tate Donovan). Plummer has invented a computer software program for missile defense that foreign governments are trying to steal, and he and his briefcase are currently being held on a speeding powerboat guarded by military personnel on board, on jet skis and in a helicopter. Shane and his crew attack and, in one of the movie’s few action sequences, take out all of the guards, freeing Plummer. Shane takes Plummer to a waiting chopper, where Plummer insists on calling his family. He opens up his briefcase by use of a voice-activated password: “Zoe, Seth, Lulu, Peter, Tyler”, revealing only a photo of his family, which he shows to Shane. As Shane goes aboard the helicopter to tell the pilot to wait for Plummer, only to find that the pilot is dead. Shane and Plummer are then shot by a barrage of gunfire, which only Shane survives.
Months later, Shane is being released from the hospital, clearly depressed about his failure. His C.O., Capt. Bill Fawcett (Chris Potter), tells him that he is being assigned to the most important duty available right now: babysitting the Plummer children while Julie Plummer (Faith Ford) goes to Switzerland with Capt. Fawcett to retrieve the contents of a safe-deposit box that her husband had opened there. Julie has complained of night prowlers, and Shane is assigned to keep the children safe while also looking for the software program, if it is hidden in the house. Capt. Fawcett also tells Shane that even the best lose someone sometimes, and starts to tell about Shane’s dad. Shane cuts him off.
The Plummer household, in Bethesda, Maryland, is chaotic six months after Howard’s death. The youngest, Tyler (a baby), and the next youngest, Peter (a toddler), are being cared for by a nanny, Helga (Carol Kane). The older kids, Zoe (Brittany Snow) and Seth (Max Thieriot), are rebellious. They also have a pet duck, which bites Shane’s ear.
Expecting Julie to return in 48 hours, Shane installs security equipment in record time and immediately catches a prowler … who turns out to be a boy sneaking up to Zoe’s room. The incident sets off both a security alarm and flashers, and the next-door neighbors, a Korean couple named the Chuns (Denis Akiyama, Mung-Ling Tsui), complain to each other about the noise and the lights in Korean. Shane, also in Korean, promises to reduce the disturbance. Back inside, Lulu (Morgan York) tells Shane that her father had told Peter a story about a ghost in the house, which Shane takes to mean that “ghost” is important. We also see that Helga does a crazy dance to help Peter fall asleep.
The next day, Shane marches the family downstairs at 6 AM. He tells them that he doesn’t have time to learn their names, so they will be “Red Leader” (Helga), “Red One” (Zoe) through “Red Four” (Peter), and “Red Baby” (Tyler), and he clamps security bracelets on all of them. When Seth isn’t there to get his bracelet, Shane breaks Seth’s bedroom door down, only to find that Seth is in the bathroom.
At the Swiss bank, Mrs. Plummer and Capt. Fawcett present their identification. The banker tells them that Mr. Plummer also set a password for the account, which Mrs. Plummer must present. Their first guess, “the ghost,” is rejected, and they decide to stay and think about possible passwords.
To get even with Shane, Zoe and Seth brush oil on the top two steps, only to be foiled when Shane reverses direction. Instead, Helga goes down the steps first, slips and crashes to the bottom. Helga promptly quits, and Shane’s efforts to stop her from leaving are foiled by a phone call from Mrs. Plummer, wanting to know how things are going.
The next day, Shane gives the kids (even the baby) military MREs (“meals ready to eat”) for breakfast. They don’t touch the “food,” and Peter finally pulls the tablecloth to the ground. Lulu shows that she can make Tyler cry at once by crossing her eyes. Shane is alone with all the kids getting ready for school, when he gets a phone call from the school threatening to suspend Zoe and Seth if they are tardy again and ordering them to report to the principal’s office when they arrive. Then Tyler’s diaper has to be changed, and the kids scatter. Shane changes it as if baby poop were radioactive. The kids are sure they’re going to be late, but Shane says, “Not on my watch,” and drives crazily to get them to school just in the nick of time.
In the principal’s office, Murney (Brad Garrett), the vice principal/wrestling coach, mocks Shane as a “babysitter,” notes that Seth has missed virtually all wrestling practices and Zoe has missed virtually all driver’s ed classes, and challenges Shane to a wrestling match … when he is suddenly interrupted by the arrival of the principal, Claire Fletcher (Lauren Graham). She dismisses Murney after making him look like a blowhard, allows the kids to leave for class, and then tells Shane that she spent four years in the Navy in California to pay for her college. She knows all about Shane’s real job from Mrs. Plummer, and it’s clear that she and Shane are attracted to each other as they exchange Navy slogans.
At school, Shane sees other kids on the playground picking on Seth and goes to rescue him, only to have Murney say that it was a good learning experience for Seth (who Murney calls “The Creeper”) to be picked on, since he’ll be picked on his whole life; after Murney leaves, Seth gets angry with Shane for interfering. Shane also sees Zoe parallel-parking in driver’s ed, where she causes an accident with a panic mistake, resulting in another trip to the principal’s office. Later, while on the playground watching Tyler and Peter, Claire comes out to see how Shane’s doing … when the alarms for “Red One” and “Red Two” go off. Shane takes off, leaving the two children with Claire, and follows the tracking beacon right into the sewer … where he finds the bracelets tied together with a card saying “Ha ha” attached to them.
Shane returns to the house covered in poop with the bracelets, where he finds Claire waiting with the kids. Claire leaves, offering to help in the future while recoiling from his stench. Shane goes to get showered and comes downstairs wrapped in only a towel. He hears giggles and turns to see Lulu and her “Firefly” troop meeting in the kitchen. They are supposed to go sell cookies outside a local Costco, and Mrs. Plummer was supposed to take them, so Shane has to do it.
The Fireflies set up a table outside the store, and Shane goes inside to shop. Then a group of boy Junior Grizzlies show up and trash the Fireflies’ cookies and table, and the Fireflies run off to hide. When Shane comes out, he finds the boys breaking up the cookies, with the girls cowering behind a car in the parking lot. Shane won’t retrieve their cookies, but the girls insist on being taken for dinner before going home.
When Shane finally gets home, he sees that the Plummer house has been turned into a party center, with kids streaming in. Shane goes inside and finds that the house is a wreck. He tells everyone that the party’s over, and it’s time to clean up. As the kids start to bolt, Shane grabs them and physically intimidates them into becoming a clean-up crew. While checking on their work, Shane finds a DVD-R marked “Ghost” and pockets it, while two hooded, black-clad figures outside the window watch him. Meanwhile, after the guests turned clean-up crew leave, Zoe screams at Shane about ruining her life, while Shane screams at her about letting kids who have no respect for her or her house trash the place. Then the black-clad figures break in through an upstairs window. Shane fights them, while the kids hide (except, at first, for Lulu, who gives him a couple of brooms to use against the invaders’ sticks). Shane does defeat the invaders in the children’s playroom, making use of several toys in new ways, but the invaders manage to escape from the house and flee. Zoe realizes that someone really is after them and promises to cooperate from now on. And Shane inserts the “Ghost” DVD-R into a computer … only to find out that it is a recording of the movie Ghost, not a software program.
At night, Peter won’t go to sleep, and Seth tells Shane that the only way to get Peter to go to sleep is to do a crazy song and dance for him called the “Peter Panda Dance” that Mr. Plummer had made up. This is the dance that we saw Helga doing earlier. It has specific steps and specific words. Seth writes it down, and Shane stumbles his way through it. Peter warmed up to him and called him "Daddy" after saying good night. Shane gets another call from Mrs. Plummer, telling him that she’ll be gone for two weeks.
In the morning, Shane lets Zoe drive the family car to school. She makes it, with a few scares, and Lulu leaps out of the car when they arrive at school and kisses the ground, glad that she's on land. But another trip to the principal’s office with Seth comes up. It turns out that Seth had dyed his hair blonde, and in a school search, a Nazi armband was found in his locker. Murney thinks “the Creeper” is joining the Aryans. Seth won’t talk about it, and Claire reminds Shane how serious this is.
When the family gets home, Seth sneaks away. Shane follows him, leaving Zoe in charge. Seth boards a bus, and Shane grabs Lulu’s little bicycle and rides off to follow it. Seth gets off the bus and, in an alley, meets other kids wearing Nazi armbands, while Shane watches from the shadows. Seth goes into a building … where Shane learns that Seth is playing the telegram boy (and Nazi wannabe) Rolf in ‘The Sound of Music.’ Seth screws up, and the director quits. Shane comes out of the shadows and volunteers to direct the production, convincing the actors that he’s a leader. He asks Seth why he’s been hiding his acting, and Seth says that his dad wanted him to go out for wrestling, but he just wants to act. Shane tells him to tell that to vice-principal Murney.
As days go by, Shane teaches Zoe to drive in a parking lot, directs the play, takes care of the baby, responds to Lulu’s tracker alarm (to learn that she was showing off his quick response as part of “show and tell”), teaching the Fireflies kung fu and learns all the kids’ names. Then Murney makes a big scene in the school grounds when he catches “The Creeper” dancing under a tree. After a prod from Shane, Seth quits the wrestling team. Murney calls Seth a quitter. Shane jumps in. Murney and Shane end up agreeing to meet in the gym for a grudge wrestling match at 3 PM. The students circulate a note about it, and the gym is packed when Shane arrives, dressed in his usual T-shirt and khakis. Murney is in a wrestling uniform, being cheered on by his team and cheerleaders. He charges Shane, who knocks him flat, then twists his arm into various positions, including “the Chicken Wing” and Shane’s favorite, “the Pacifier,” in which Murney’s fingers are stuck in his mouth. Finally, Shane pins Murney, with Seth signaling the pin.
Zoe gets her license, and Seth gets better at his part. Lulu and her Fireflies go back to Costco to sell cookies. This time, when the same Junior Grizzlies threaten them, they stand in front of their cookies and use their new kung fu skills to beat the boys up and tie them to pillars with their own neckerchiefs.
Back in Switzerland, the bankers still are waiting for the password. Mrs. Plummer and Capt. Fawcett say they’ve tried everything they can think of. Then Julie takes off her wedding ring and notices the inscription “My Angel” inside. She tries that as the password. It is. They get to open the safe-deposit box, where they find a two-pronged key.
Shane gets better at the Peter Panda song, which he now knows by memory. Peter says, “Good night, Daddy,” to him. Shane sees Zoe outside, sitting on the window sill, and asks her what’s wrong. She talks about her father. Shane talks about his father, who was in special ops like himself, and who basically abandoned his son. He talks about how he always wanted a family. And just when Shane’s feeling connected to this family … Mrs. Plummer calls and says she’ll be back tomorrow. The kids hug and celebrate, without Shane.
Shane’s preparing to fix Seth’s door before he leaves. While working in the garage, he sees the duck’s foot caught in a grate in the corner. The grate turns out to lead to a secret underground cavern, which leads to a security door that needs a two-pronged key to open. He immediately calls Capt. Fawcett, who is with Mrs. Plummer preparing to leave Switzerland, and who reacts somewhat inappropriately (although Shane doesn’t notice).
When Mrs. Plummer returns home and opens the door, she hears the song “The Sound of Music,” as sung by the children in that play to welcome their father back from Vienna. She then sees a brochure for the play, picturing Seth playing Rolf. As she walks further in to the house, she sees her children waiting for her and Shane playing the song on a CD. Shane goes out to the garage with Capt. Fawcett.
Capt. Fawcett offers Shane his choice of duty after this one. Shane says that he’s not sure he wants to continue in the SEALs … when suddenly the next-door neighbors, the Chuns, walk in the garage wearing black ninja suits with guns drawn. They were the ones who had broken in to steal “Ghost.” Shane swiftly disarms them and has guns drawn on both, when he is clobbered in the back of the head with a gun butt wielded by Capt. Fawcett.
In the house, Capt. Fawcett and the Chuns are tying up and gagging the kids. Mrs. Plummer calls Capt. Fawcett a traitor. Mr. Chun is left to watch the kids, while Mrs. Chun and Capt. Fawcett take Mrs. Plummer and the key to the vault. The vault opens, but the safe is on the other side, and the center of the vault is guarded by various security devices.
Meanwhile, Zoe and Lulu untie their bonds without Mr. Chun seeing. Then Lulu crosses her eyes at baby Tyler, who starts bawling on cue. While he distracts Mr. Chun, Lulu unties Seth. The kids then jump Mr. Chun, knock him out and take off for the garage, where they find an unconscious Shane. They wake Shane up and tell him the situation; he tells the kids to take off and get help while he tries to rescue their mother.
Shane goes down to the vault, where Capt. Fawcett is just about to kill Mrs. Plummer if she doesn’t tell how to get through the vault. Shane interrupts and tries his hand at it. He says the names of all five kids, which Howard did with the briefcase. No luck. He thinks for a moment. Then he tries doing the Peter Panda song and dance. Turns out that the steps of the dance are the way – the only way – to get through the vault security devices.
Zoe and Seth forgot their cell phone, and they’re trying to get help. Zoe sees a cop car and speeds past it, and it pulls out to follow her, sirens flashing. She drives past the school, where Claire and Murney, standing next to each other, see her being chased by two police cars.
After Shane gets to the other side of the vault, he turns the security system off. Mrs. Chun and Capt. Fawcett argue about who should try to open the safe first. As they argue, Shane quickly disarms them, only to have Fawcett pick up his gun and point it at Shane again. Finally, as he is about shoot Shane, Shane says, "Good night, Peter Panda", and the metal door of the safe opens up, knocking Fawcett out. Mrs. Plummer then slugs Mrs. Chun when she recovers.
Zoe’s car and the chasing police arrive in the driveway. The kids run from the car toward the garage, with the police in hot pursuit, when Shane and Mrs. Plummer come up from the vault. The police make everyone put their hands up. Then a machine-gun-wielding Mr. Chun tells the police to drop their weapons and put their hands up too. The police comply. Just then, Claire shows up at the end of the driveway, behind Mr. Chun, and signals to Shane that she’s going to try to jump Mr. Chun from the side. While she’s moving into position, Shane tells the duck to attack Mr. Chun, and it bites him the crotch. Claire jumps Mr. Chun from above, subduing him.
As the police are wrapping up, Claire asks Shane if he’s leaving now that his mission is done. He equivocates and says that he’s still got at least one more thing he has to do before he goes (meaning the play), before they are interrupted by the police. Before they share a kiss, Lulu pops up and tells Shane that she’s afraid that he’ll forget her, which he promises not to do, and she gives him the same picture of the family that Howard Plummer was carrying back at the beginning. Of course, there's one more mission to finish.
Finally, it’s opening night for The Sound of Music. Everyone is in the audience, including all the Plummers and Claire. Seth performs his part flawlessly. Claire comes backstage to talk to Shane, who is clearly thinking about staying. She tells him that the school has an opening for a wrestling coach, now that Murney has found his true calling. As they prepare to kiss, they see Murney in the end scene of the play, singing off-key while dressed in a nun’s habit.
