When local police foil an attempted terrorist attack on a concert, it comes as a huge shock to discover that the supposed terrorist is none other than forensic scientist extraordinaire, Abby Sciuto. When Gibbs and the rest of the team responds to her aid, she explains that the "attack" was actually just a think tank exercise and that none of it was real. Unfortunately, it doesn't take long to realize that she was actually playing with real explosives and real sarin gas, much to her shock. It seems that the beloved scientist was unwittingly being used to stage an actual terrorist attack. It doesn't take long for the team to track down the rest of her fellow members of the think tank, but they are just as in the dark as Abby is regarding what went wrong. To make matters worse, the Homeland Security agent who organized the think tank exercise is nowhere to be found, and everyone begins to suspect that he's behind everything. But is there something more at play? Is the agent actually responsible for the attack? And what happens when a critical terrorist response playbook is stolen? Find out what happens when you watch NCIS Season 14 Episode 15 online!