A U.S. State Department employee, Kate Abbott, newly assigned to the American embassy in London, is tasked with identifying potential terrorist threats. During her meticulous vetting process, she begins to uncover anomalies that point toward a larger, more sinister plot. Her suspicions are confirmed when a bomb attack targets her team at a restaurant, leaving her as the sole survivor and primary suspect. Realizing she's been framed, Kate must prove her innocence while evading capture by both U.K. authorities and the true perpetrators.

As she digs deeper, Kate discovers that an elusive and deadly assassin known as "The Watchmaker" has been hired to eliminate anyone who threatens the execution of an impending terrorist attack planned to happen on New Year's Eve in Times Square. Her pursuit of the truth turns into a race against time across London as she attempts to thwart the catastrophic plot. Along the way, Kate faces numerous close calls and betrayals, but her relentless determination drives her to push through for the sake of countless lives at stake.