When a Marine's body surfaces halfway around the world, the investigation forces Ziva to dig up a lost chapter of her life.
A corpse discovered at the bottom of a gorge forces the lab into lockdown when it begins to discharge an unknown substance.
Callen goes undercover to infiltrate a network of Chechen terrorists that are recruiting foreign fighters to join their cause, an attack in the US.
Huck quickly determines that Amanda Tanner was kidnapped; when a plane crashes in suspicious circumstances, killing all the passengers, including a US senator, Olivia is tasked with representing the pilots.
A national tragedy forces Olivia to return to work at the White House. Meanwhile, we learn more about the first few days of Fitz's presidency.