Jack is back, this time in New York City spending time with his granddaughter. However, when a former contact comes to him with vital information on an upcoming terrorist assassination attempt, Jack has no choice but to become involved and take the man to CTU. But to get to CTU, they first need to survive a whole bunch of terrorists all trying to kill them. Meanwhile, Chloe struggles to settle in at her new position at the upgraded CTU, and President Allison Taylor negotiates with Middle Eastern leader Omar Hassan over weapons inspections... unaware that Hassan is the assassins' target. Also, a journalist named Meredith Reed is suspected to have direct ties with the on-going terrorist crisis.

While the newly-upgraded CTU is challenged by some unexpected and complicated circumstances, Jack Bauer becomes even more involved in preventing an upcoming assassination attempt on Omar Hassan, a visiting President. Meanwhile, international security is jeopardized by an explosive event, and Jack is reunited with agent Renee Walker.

With only four hours left, a rogue Jack Bauer stops at nothing to determine who is behind the day's most devastating events, and he uncovers an unexpected lead.