Still grieving the death of her husband Peter one year ago, single mother Amy Carr sees her young daughter Emily off to elementary school. She then tries to have a moment with her distant and depressed teenage son Noah, but Noah dismisses Amy as well as her suggestion to get out of bed and go to school.Amy goes for a long run in the woods. While jogging, Amy makes and takes various phone calls with her boss Greg Minor, Mrs. Sandra Fischer at her daughter's elementary school, her mother, her friend Heather Euclid, a contractor, and a mechanic named CJ at an auto body shop.An emergency alert warns Amy of a shooting at her son's high school. Amy repeatedly tries to call Noah, but her messages and texts go unanswered.Amy calls 911. Operator Dedra Wilkinson advises Amy to get to a staging location for concerned parents at a community center. Unable to find an available ride among her friends, Amy begins jogging to the location but sprains her ankle.Through a series of phone calls with previous contacts, Amy confirms Noah's truck is at the school, indicating he did leave the house after all. Since his auto body shop is near the police barricade, CJ acts as Amy's eyes and ears at the scene, and he tells Amy that the police are searching Noah's truck.Amy trips and hits her head on a rock. Continuing to walk while dizzy, Amy begins wondering if her son is the shooter. 911 operator Dedra puts Amy in contact with Detective Ed Paulson. Although the detective refuses to provide concrete information, he asks questions about firearms and mental health that imply Noah could be the shooter. Amy leaves another message for Noah asking him to stop if what the authorities are saying is true.CJ calls to tell Amy that the police are searching additional vehicles. Noah also calls with a plea for help before being cut off by a commotion.Amy calls Dedra at 911 to tell her about Noah's call. Detective Paulson confirms Noah is not the shooter. Paulson explains that Noah and the shooter are among five people barricaded inside the high school's chemistry lab. However, Paulson refuses to reveal anyone's identity.Amy calls CJ to get the license plates of the other cars being searched by police. Using his auto database, CJ subsequently texts Amy with the registration info for each vehicle.Amy calls Heather and asks to speak to her daughter McKenzie, who safely evacuated the high school. McKenzie recognizes all of the names Amy asks about except Robert John Ellis.Amy calls her boss Greg at his tax office. Amy convinces Greg to look up Robert's tax records in order to obtain his phone number. Amy also learns Robert used to work in the high school's cafeteria.A Lyft driver she called previously finally finds Amy on a forest road. During her ride toward the school, Amy checks Robert's social media accounts and confirms he is unstable.Amy calls Robert directly. Amy identifies herself as a hostage's mother, but Robert suspects she is working with the police. Amy pleads for the lives of the hostages and offers to help before the call cuts off. Paulson calls Amy to admonish her for contacting Robert, and warns her not to call him again.Amy calls 911. Paulson joins Amy's conversation with Dedra. Paulson explains that Robert abruptly stopped all negotiations, so the police now need Amy to distract him while a SWAT team breaches the chemistry lab. Amy does as asked, but Robert cuts off her call again.Amy arrives at the school. Noah calls Amy. Amy is on the phone with her son as the raid happens and multiple shots are heard. Noah's call cuts off. Although initially concerned her son might be dead, police safely escort Noah across the barricade to reunite with his mother. (thanks to culturecrypt)