Ryan (CHRIS EVANS) is a twenty-year-old who's just been dumped by his girlfriend Chloe (JESSICA BIEL) who sees him as going nowhere in his life. While strolling through Santa Monica with his friend Chad (ERIC CHRISTIAN OLSEN), Ryan runs into Chloe and tries to prove that he's changed by volunteering to help her with her environmental cause. On the way to the store, however, his cell phone rings and his day becomes severely sidetracked.
On the other end is Jessica Martin (KIM BASINGER), a high school science teacher who's just been kidnapped by a bunch of armed thugs who've shot her housekeeper dead and taken Jessica to an unknown location. Their angry leader, Ethan (JASON STATHAM), wants something he claims that she or her husband Craig (RICHARD BURGI) possess, but she has no idea what he's talking about.
In their absence, she's partially managed to reconnect a smashed telephone and the connection went through to Ryan. He, of course, thinks it's a crank call until he hears Jessica's next encounter with the kidnappers. Accordingly, Ryan races to the local police department to report the abduction and hands over his phone to Sgt. Bob Mooney (WILLIAM H. MACY). A 27-year veteran, he's about to retire and open a day spa with his wife, much to the amusement of his boss Jack Tanner(NOAH EMMERICH).
A small riot in the station results in Mooney handing the phone back to Ryan. But when the signal starts to fade in the building -- and with both parties knowing the connection might not ever be reestablished if broken -- Ryan races off to try to beat the kidnappers to Jessica's son, Ricky (ADAM TAYLOR GORDON), who's just getting out of school.
As things become more perilous for Jessica on the other end of the line, and Mooney begins to become suspicious of what previously occurred, Ryan does what he can to help her and her family, all while dealing with increasingly frustrating and dangerous developments and trying to keep that phone line live.