A mentally disturbed man starts shooting on a train, and a Navy officer and a fellow passenger work together to take him down. The Good Samaritan doesn't stick around to get praises, however. The team eventually IDs the Samaritan as Corpsman Nolan Griffith... who was captured by the enemy in 2012 and had never been found.
They speak to a CIA agent, Calloway, who claims that they didn't know Nolan was alive until they called, and they were suspicious of his motives for being in New Orleans. When they raid Nolan's house, they spot him and realize that he's with Aman Bashir, a Pakistani terrorist.
They are later able to capture Nolan, who says that Bashir is planning a terrorist attack and that they must release him to help stop it. He claims that he's working undercover with Calloway as his handler. Calloway turns up dead, stabbed to death, and is unable to support his claim.
Pride decides to trust him, and releases him. Nolan gives them the slip, however, and rejoins Bashir. They go to a hotel, where an internation summit is taking place.
The team corners Bashir and another terrorist, who were preparing to assassinate the keynote speaker. Nolan sees Bashir reaching for a grenade and kills him.
Nolan is happily reunited with his sister, his wife, and his young baby.