On September 11, 2001, Port Authority police officers John McLoughlin and Will Jimeno are on patrol at the Port Authority Bus Terminal in Midtown Manhattan when they witness a plane flying dangerously low in the sky. Shortly after returning to the station, they catch a glimpse of the TV, revealing the horrifying news that a plane has struck the North Tower of the World Trade Center. Sgt. McLoughlin quickly organizes many officers to assist in the evacuation of the still undamaged South Tower, utilizing a commandeered Metropolitan Transit Authority bus. Their hearts sink as they hear reports indicating that the South Tower too has been targeted.

Upon arrival at the chaotic World Trade Center site, the officers are confronted with the terrifying reality of the disaster, including seeing one of the first jumpers from the towers. As Jimeno distributes their police gear at 5 World Trade Center, the team—comprising McLoughlin, Jimeno, Dominick Pezzulo, and Antonio Rodrigues—prepares to enter the concourse between the towers. They receive information from officer Chris Amoroso regarding the attack on the Pentagon and the subsequent hit on the South Tower; however, the group initially dismisses the severity of the situation.

Just as the team readies themselves to enter the North Tower, ominous rumblings fill the air, signaling the imminent collapse of the South Tower. In a desperate bid for survival, they rush towards the service elevator shaft, but the chaos ensues—Chris falls and cannot recover, and Rodrigues is unable to make it to safety in time. McLoughlin, Jimeno, and Pezzulo manage to escape the swirling dust and debris, but as more rubble descends upon them, they become trapped in the debris-laden elevator shaft.

After the avalanche of debris begins to settle, Pezzulo finds a way to free himself and makes his way closer to Jimeno, who remains pinned alongside McLoughlin. Despite his efforts, Pezzulo cannot shift the debris covering Jimeno’s legs and heeds the desperate warning from McLoughlin not to abandon them. Just as Pezzulo feels a flicker of hope for survival, the rumbling continues as the North Tower also crumbles. While Jimeno and McLoughlin escape further injury, Pezzulo suffers a grave fate. In a final act of desperation, he discharges his weapon through a gap in the debris to signal for help, succumbing to his injuries soon after.

Amid the silence and darkness, Jimeno and McLoughlin endure hours pinned beneath the wreckage, sharing personal stories and striving to keep each other awake. The nurturing camaraderie grows as they cling to hope, with Jimeno discovering that by straining to grasp a metal bar overhead, he could create noise that may draw rescuers near. Miraculously, two U.S. Marines, Dave Karnes and Marine Sergeant Thomas, searching through the ruin, hear their calls for assistance.

Rescue operations proceed with Jimeno being the first to be extracted from the debris, followed by McLoughlin, who is pulled out later, barely clinging to life. The two officers are eventually reunited with their heartbroken families in the hospital, a testament to their resilience and the importance of unity in the face of overwhelming adversity.