Plot
U.S. Navy SEAL lieutenant Shane Wolfe is assigned to rescue Howard Plummer, a man working on a top-secret government project, from a group of Serbian rebels. Shane and his team successfully get Plummer off an enemy boat. Boarding the helicopter to escape, the team is attacked and Plummer is killed. Shane spends two months in the hospital recovering from gunshot wounds to the chest.
At the United States Naval Academy in Annapolis, Maryland, Shane's commanding officer, Captain Bill Fawcett, explains that he has been assigned to escort Plummer's widow, Julie, to Zürich, to retrieve the contents of Plummer's safety deposit box. Meanwhile, Shane has been assigned to stay at the Plummer residence in Bethesda, Maryland, to search for the secret project called GHOST and mind the family's five children: Zoe, Seth, Lulu, Peter, and baby Tyler. The kids prove to be difficult to handle, even with the help of nanny Helga, who quits when one of Zoe and Seth's pranks intended for Shane goes wrong, with Helga suffering the prank instead. Shane eventually begins to discover the children's problems and resolve them, gaining their trust after saving them from a pair of armed ninjas looking for the GHOST program.
Later, the school's vice principal, Duane Murney, informs Shane that Seth has cut and bleached his hair, has a Nazi armband in his locker, and has skipped a month of wrestling practices. At home, Seth tells Shane he only joined the wrestling team because of his father. After Seth sneaks out of the house, Shane follows and learns that Seth has secretly joined an amateur production of The Sound of Music , playing the role of Rolf. The director quits, and Shane takes charge of the show, takes care of the house, gives Zoe driving lessons, and teaches Lulu and her fellow Firefly Scouts martial arts to defend themselves against rival scouts.
As Seth quits the wrestling team, Shane challenges Murney to a wrestling match in front of the entire school, which he easily wins despite Murney's show of bluster. The Firefly Girl Scouts use the fighting skills that Shane taught them to fight and tie up the rival Boy Scouts. Zoe and Shane share stories of their fathers, both of whom had died in similar circumstances, and both hug. They are interrupted by a phone call from Julie, who has figured out the password "My Angel," retrieved a two-prong key from the box, and is on her way home. The kids immediately plan a "Welcome Home" party for her.
That evening, Shane discovers a secret vault underneath the garage, which requires the key Julie just acquired. When Bill and Julie arrive home, he and Shane go to the garage, where Shane says he is rethinking his career. The two ninjas from before arrive and pull off their masks, revealing themselves as the Chuns, the Plummers' North Korean next-door neighbors. Suddenly, Bill overpowers Shane and knocks him out, revealing himself to be a double agent working with the Chuns. After Bill ties up and gags the children, Mr. Chun holds them hostage in the playroom while Bill and Mrs. Chun take Julie down to the vault. They open the door, but a dangerous security system prevents them from proceeding, with one of the traps burning off Mrs. Chun's eyebrows.
The children escape, take down Mr. Chun, and wake Shane, who sends them to get help while he goes to the vault to help Julie. Mr. Chun follows them in Bill's car. With Zoe at the wheel, the kids force him to crash. Shane gets past the security system using the dance Howard had used to lull Peter to sleep each night. Julie knocks out Mrs. Chun, and Shane's voice activates the final vault, opening the door which knocks Bill unconscious. By then, the children have lured a large crowd of police (including the FBI) to the house. Mr. Chun arrives and holds all of them at gunpoint. Shane notices the school principal and his love interest Claire Fletcher right behind him, having followed the chase upon seeing it pass the school. Shane distracts Mr. Chun with the help of the family pet duck Gary, and Claire knocks him unconscious.
Bill and the Chuns are arrested, and Shane and the Plummers say their goodbyes. At Seth's performance, it is revealed that Shane has retired from the Navy and joined the school staff as the new wrestling coach. Murney, dressed as a nun, also performs in the play, singing "Climb Ev'ry Mountain" off-key, and Claire and Shane kiss backstage.
