Cellular

Science teacher Jessica Martin lives with her husband Craig and son Ricky. One morning, intruders break into their home, killing their housekeeper and kidnapping Jessica. They lock her in an attic, smashing the landline. She wires the broken phone to try to connect to someone.
She manages to connect to Ryan, a laid-back, immature young man hanging with friends at Santa Monica Pier. Although believing Jessica is pranking him, he goes to the police. When a fight erupts at the station, he is sent upstairs to report the kidnapping. However, worsening cell service on the way up forces him to stop so he doesn't lose Jessica on the call.
Lead kidnapper Ethan Greer demands Jessica reveal Craig's location. When she refuses, he goes after Ricky. Overhearing Ethan threatening Jessica, Ryan realises the kidnapping is real, which sobers him. He is unable to prevent Ricky's abduction. Due to low phone battery, he uses a gun from a security officer's car to skip the store line and quickly obtain a phone charger.
Investigating Ryan's claim, Officer Mooney visits Jessica's home. One of Ethan's accomplices, Dana Bayback, poses as Jessica. When Ethan returns with Ricky, Jessica helplessly reveals that Craig is at an LAX bar.
A cross-connection between cell lines forces Ryan to steal a nearby lawyer's car and cell to not lose Jessica. Ryan plants the gun on one of the kidnappers at LAX to alert security and is shocked to learn the kidnappers are LAPD officers. They nab Craig while Ryan loses the lawyer's car to the impound. Mooney sees Ryan on the TV news for the car jacking, calls Jessica's home again, and realizes he was deceived by Dana.
The kidnappers take Craig to his bank safe deposit box for a video camera bag, which Ryan intercepts. While Ethan chases him, the lawyer's cellphone shatters and Ryan loses connection with Jessica. He watches the reason for Jessica and Craig's predicament: an incriminating video on Craig's camera of LAPD detectives Ethan, Mad Dog, Dimitri, Dana, Deason, and Mooney's colleague Jack Tanner robbing and murdering two drug dealers.
Stealing the lawyer's car again from the impound, Ryan finds his own cell that he'd dropped in the seat. Mooney returns to the Martins' and kills Bayback in self-defense. Mad Dog discovers Jessica has been using the landline and tries to kill her. She nicks his brachial artery, so he swiftly bleeds out, though Ethan stops Jessica and Ricky from escaping. Ryan contacts Ethan, offering the videotape in exchange for the Martins at Santa Monica Pier.
There, a disguised Ryan demands the Martins are freed before surrendering the videotape, but his ex-girlfriend Chloe inadvertently reveals him. Tanner sends Mooney away with Dimitri and takes Ryan hostage. Ethan destroys the videotape, then radios Deason to kill the Martins at the safe house. Mooney overhears and realizes the truth. He overpowers Dimitri while Ryan escapes to a boathouse. He knocks Tanner out, but Ethan overpowers him before Mooney appears. After a brief altercation, Mooney is able to shoot Ethan dead with Ryan's help.
Jessica strangles Deason with her handcuffs in the van, then frees Craig and Ricky; he attempts to kill them. Ryan saves them by knocking Deason out. Tanner's part in the scheme is exposed, as Ryan had copied the video on his cell. Jessica finally meets Ryan in person, the man who risked his life to save her family, and thanks him, asking if she can do anything for him. Ryan jokingly asks her never to call him again.