The film opens with a sweeping view of the Lower Manhattan skyline at dawn on September 11, 2001. Michael is a bicycle courier who takes a moment to wish his young daughter a happy birthday before starting his delivery route. Metzie stops for a coffee at a bustling café, then heads toward the North Tower, where she works as an elevator dispatcher. At 8:00 am, Jeffrey Cage and his wife, Eve Cage, a billionaire trader and his estranged spouse, meet in the North Tower’s law offices to sign divorce papers, sparking a tense personal moment amid a looming catastrophe.
When American Airlines Flight 11 slams into the 93rd–99th floors at 8:46 am, the elevator carrying the trio—[Michael], [Eve], and [Jeffrey Cage]—stops around the 38th floor, and its electronic systems fail. Also inside the car are Eddie, a maintenance man, and Tina, a woman who has come to the World Trade Center to end a relationship with her wealthy lover. They quickly realize escape is impossible through the stuck doors because of a security locking system.
From the elevator dispatch center, [Metzie] guides them via the public address system, telling the group that their only chance is to force the door open and send [Eddie] to the power room to rewire the elevator. The passengers brainstorm makeshift plans to pry the door loose. They try using their hands, but the door remains stubbornly shut, and the emergency shaft above can only be opened from the outside.
[Metzie] informs them that firefighters cannot reach the top floors, so the group must unbolt the locking mechanism to free themselves. After a tense sequence of efforts, they finally pry the door, and [Eddie] manages to unlock the mechanism with a screwdriver and break through a block of drywall into a janitor’s room. [Eve] makes it out first before the elevator begins to descend due to broken cables, leaving the others trapped behind the failing doors. [Jeffrey Cage] tells [Eve] that he loves her and promises to meet her in the lobby, a bittersweet moment amid the chaos and fear. The car hurtles toward the lobby, and the passengers brace for impact; the elevator speeds down, and while [Eve] escapes with injuries, the others survive with injuries as well.
A firefighter reaches the top of the stalled car and opens the emergency shaft, extending a hand to [Jeffrey Cage] as the North Tower begins to crumble around them. The sequence culminates in a fatal moment for one member of the party as the building collapses, leaving the others to confront the aftermath of a day that changed the city forever.