A man with a metal detector finds a severed hand on the beach. Callen and Anna are taking a trip, and FBI Agent Roundtree is filling in for him. Hetty tells Callen she didn't help get Anna exonerated. Fatima gives Roundtree a tour of the office. Nell tells Kensi she plans to resign from NCIS. Kensi urges her to take some time off instead. The hand belongs to David Larian, an Iranian exile looking to overthrow the current regime. Hetty is cool when introduced to Roundtree. Nell hides from Eric but runs into Hetty, who is burning passports. Hetty asks if there's anything on her mind. Deeks and Roundtree find Larian's car. Roundtree sits down and activates a bomb in the glovebox. Sam's plan involves freezing the bomb with liquid nitrogen to slow it down. Then Sam sets up a pulley and attaches the rope to himself and Roundtree, jumping off and pulling out Roundtree before the explosion. Sam takes Roundtree with him and sends Deeks back to the office. Kensi has a heart-to-heart with Fatima. Sharian's daughter Roxie, who is armed, flees from his office with files with Kensi and Fatima showed up. Sam has Roundtree interrogate Dr. Shahmir Gilani. Fatima questions Roxie. Neither gets too far. Deeks is tailing Roxie, as is another vehicle. Two men try to snatch her, but Deeks shoots one and captures the other. Larian's torture and murder were recorded on one of their phones. Nell pinpoints the house where the men stayed. A bombmaker lives there and the house is boobytrapped. Sam shoots and kills the bombmaker and grabs his dead-man's switch. Hetty drinks with Nell. Hetty knows Nell wants to resign and encourages her to use her vacation days first before resigning. She takes out Eric to tell him.