A bomb goes off in a fish market and NCIS is tasked to find out if it's terrorism related or not. They find a DEA agent, Talia, is working undercover investigating the possibility of drugs moving through the market. Talia is poisoned in the aftermath of the explosion, but Sam recognizes the symptoms and is able to save her.
There wasn't any footage of the bomb being left, but they were able to track the man who poisoned Talia. They track down Raul. He seems to be clean, but when Hetty runs his face through a Middle East database, he comes up. Raul is a fake identity. He's a terrorist.
They also tracked Talia's suspect, Mateo. Talia and Deeks finds his car. Test show signs of a chemical used for septic tanks. The terrorists were planning to attack a gathering using a septic truck. Sam, Callen, Deeks and Talia prevent the attack, though the truck explodes in a parking lot.
In Afghanistan, Kensi tracks the White Ghost. It's not Sabatino. When he's unmasked, Kensi recognizes him and isn't able to take the kill shot. She misses him on purpose, returns to base, and lies to Granger about his identity.