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….

Jack Bauer becomes further involved in preventing an assassination attempt on visiting president Omar Hassan. As the crisis continues to escalate, the crew at the newly upgraded CTU is challenged…

For the first time in New York City, Jack Bauer is reluctantly drawn into action as President Allison Taylor negotiates plans for international security with Middle Eastern leader Omar Hassan….

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…

Derek asks Addison to work with his pregnant patient while Archer recuperates from surgery; Bailey and Naomi work together to find the cause of Sam’s sudden asthma attack; Cooper, Violet…

Addison, Naomi and Sam rush the ailing Archer to Seattle Grace and reunite with old friends Derek and Mark to help save his life; meanwhile, Izzie employs her fellow doctors…

Derek’s confidence is shaken like never before as he faces off with Addison over what course is best for their dying pregnant patient; Cristina calls the abilities of a renown…

Now that Derek has the engagement ring, he searches for the perfect way to propose to Meredith, as Lexie demands that Mark go public with their relationship, and Bailey, encouraged…