Matt Biedel

After a mysterious illness strikes children from military families, Gibbs and the team investigate the cause. Meanwhile, Abby and Jimmy partner with the Naval Medical Research Center to determine the strain of illness, all in hopes of delivering a cure before the holidays.

The NCIS team partners with Homeland Security after the murder of a Navy master diver is linked to chatter of a foreign attack on the city.

When Sylar (Zachary Quinto) comes face-to-face with his long lost father (guest star John Glover), the reunion proves to be what he least expected. Elsewhere, after receiving a tip from "Rebel," Claire (Hayden Panettiere) must decide if she will help her sworn enemy, Eric Doyle (guest star David Lawrence XVII), evade capture. Meanwhile, as "The Hunter" (guest star Zeljko Ivanek) plans to uncover the Petrelli family's secrets and take control of Nathan's (Adrian Pasdar) operation, Matt (Greg Grunberg) finds himself in the spotlight and on the verge of leveling Capitol Hill. Jack Coleman, Ali Larter, James Kyson Lee, Masi Oka and Cristine Rose also star. Randall Bentley and Ashley Crow also guest star.

New evidence prompts the team to believe that foul play was involved in the 1999 death of a high school debate team champion. The brilliant debater from a low-income background was wrongly thought to have committed suicide after losing his first debate three months into his scholarship-funded schooling at a competitive top private high school.

Don's old flame Robin Brooks returns to California to prosecute an incarcerated criminal, but when three witnesses involved in the case are murdered, Don and his team realize that the next victim may be Robin and must work to keep her safe.