In Bucharest, U.S. Marine Gunnery Sergeant Alexandra "Ali" Gorski is on a crucial mission to safeguard a convoy that is transporting the ambassador's daughter. Unfortunately, they are ambushed by ruthless armed mercenaries. Despite Ali's fierce and effective combat skills, the attack leads to the tragic deaths of the ambassador, his wife, and their daughter. As a result, Ali decides to leave the Marines and makes her way back to New York City.
Upon her return, her uncle, Pat, informs her of a job opportunity at The Carrington Hotel, where he is employed. Ali takes the position, working alongside another doorman, Borz. It is there that Ali learns about her late sister's husband, Jon Stanton, a professor who resides in the hotel along with their two children, Max and Lily. Unbeknownst to them, Jon and Ali share a history, which leads to her invitation to their Easter dinner.
The Easter holiday takes a dark turn when Ali's uncle, Pat, meets a gruesome fate at the hands of Borz, wielding a sledgehammer; it becomes clear that Borz has been masquerading as a doorman with intent to hunt down the valuable paintings concealed within the hotel. The plot thickens when a team of mercenaries, led by Victor Dubois, descends upon the hotel and enacts a terrifying lockdown. Dubois and his crew break into the apartment of Bernard Hersch, a man afflicted with akinetic mutism. Dubois, recognizing Bernard as Erich Dreischler, demands information about the location of the paintings. When Bernard is unable to divulge the secrets after Borz's brutal tactics, the mercenaries pivot their focus to 10C, the home of the Stantons.
In a tense culmination, Dubois and his men take Jon and Lily hostage while Max narrowly escapes being captured. As the situation intensifies, Dubois stumbles upon the hidden safe containing the paintings, and in a perilous moment, Martinez is forced to employ a water-cooled drill to bypass the safe's combination. In an attempt to buy some time and help Lily, Jon engages Dubois in conversation while she tries to send an urgent message for help via social media, a move thwarted by Borz, who forces her to delete it.
As more bloodshed ensues – with the discovery of Bernard and his wife's lifeless bodies and the revelation of Borz's treachery – Ali is propelled into action, eliminating henchmen in a bid to rescue the Stantons. Alongside Max, they trigger the fire alarm in a desperate attempt to alert the fire department, but their strategy proves futile when Borz effortlessly explains it away as a false alarm. Following more fierce encounters, Max is recaptured, leading to a high-stakes standoff orchestrated by Dubois, who uses the PA system to coerce Ali into surrendering.
Utilizing her cunning, Max cleverly sends Ali a message through Morse code, which prompts her to disable the water supply feeding into the drill. The ensuing chaos results in Leo, one of the henchmen, meeting his end in a nail bomb explosion set by Ali. Dubois, clutching tightly to his ego, threatens to kill the innocent family unless his demands are met. Under duress, Ali complies and, using a corrupt NYPD officer Olsen, connects the hose from the rooftop water tank to the drill. When the safe opens, revealing the coveted paintings, tension heightens as Dubois and his crew discuss the distribution of the profits. However, Ali is far from helpless; she eliminates Olsen, seizing control, but not before Borz inflicts injuries on Jon and kills Martinez in a desperate bid to increase his own share.
As law enforcement arrives, Borz cunningly disguises himself as a doorman, attempting to frame Ali for the chaos that ensued. But Ali is not so easily cornered; she incapacitates the officers pursuing her and chases down Borz. In a dramatic confrontation within the hostile environment of the sewers, Borz turns on Dubois, leading to an intense showdown where Ali ultimately prevails, using a grenade to secure her victory.
In the aftermath, Ali bids a heartfelt farewell to Jon and his children, who are set to leave for London, marking a bittersweet end to her harrowing journey.
