Clay Riddell is a disillusioned artist, who a year earlier abandoned his wife Sharon and son Johnny in order to fulfill his dream of publishing a graphic novel. At Boston International Airport, Clay tries to board a flight, hoping to reconcile with his family. His cell phone battery dies, so he calls Sharon using a payphone. Suddenly an electronic signal (later dubbed "the pulse") is broadcast across mobile networks worldwide, turning cell phone users into rabid killers. Clay escapes the chaos in the terminal and meets a group of survivors in a subway car. The train's conductor, Tom McCourt, suggests abandoning the train and traveling through the tunnels, since power has been cut to the subway trains and the pumps keeping the tunnels dry will soon shut down with no one manning them. Clay agrees and, joined by a third man, attempts to escape the airport.
Near the tunnel's exit, their companion is slaughtered by an infected man, later dubbed a "phoner", and the two escape to the street above. Clay leads Tom to his apartment. That night, they are joined by Alice Maxwell, a teenage neighbor of Clay's who killed her mother in self-defense. All three decide to escape Boston. Heading north through New England to find Sharon and Johnny, the three acquire weapons from a house and are chased by a flock of phoners to a nearby river. Hiding from the infected, they observe the flock emitting mysterious signals from their mouths and then walking off as a group.
After sundown the three arrive at a private school, where they meet two survivors: headmaster Charles Ardai and a student named Jordan. Charles postulates that the phoners have developed a hive mind and are telepathic. He shows them thousands of phoners lying inert in the school's athletic field. Charles has a plan to use the stadium's gas pumps and a sprayer truck to burn the phoners, and the others agree to help. Clay and Tom drive over the phoners, spraying them with gasoline, which Charles sets ablaze. The fire spreads, causing an explosion that kills Charles. The remaining group, now including Jordan, continue north.
Taking shelter at an abandoned drive-in theater, the four go to sleep, and all of them dream about a raggedy-looking man in a red hoodie, a character from Clay's graphic novel. Later they encounter a group of survivors in a roadside bar. They tell the four about Kashwak, a state park in Maine where there is said to be no cell service. After agreeing to travel there, they spend the night in the bar. Sally, one of the survivors, is awoken and infected by a group outside. She can now transmit the pulse through her mouth. The group attacks Tom and Jordan. After saving Tom from a phoner, Alice is bludgeoned in the head by Sally, whom Tom fatally shoots. The group takes Alice outside, where she succumbs to her head wound.
Later, the group encounter a sleepless Ray Huizenga and his friend Denise, who say that Kashwak is a trap set by the Raggedy Man. Ray becomes increasingly agitated, mut
