Antonis Cosse a.k.a. Elias Minas is killed when a drone attacks. Minas attempts to knock down the drone, but it explodes forcing him to fall over a balcony and dies. Sierra Fisher took video of the attack on Minas' mobile phone. Minas provided information against the terrorist group, PK, and he was put into witness protection even though he was previously on the no-fly watch list. He disappeared three months before he was killed.

Nell is an expert on drones and goes with Sam and Callen to help investigate. She days the drone was not a hobby plane.

Fisher's married and not to Minas. She met him at the gym. She wants the phone back to erase photos. Sam and Callen threaten to tell the reporters about a witness in order to get her to talk. She tells them what she saw.

Before the attack, Minas went down to get coffee. He spotted a Greek National, Frank Kouris, in a car across the street. Kouris is one of the PK people Minas turned against.

Kensi and Deeks find a dead body in a dumpster. It's the garage owner.

Sam and Callen follow Kouris to a restaurant. Callen shows up to the restaurant as a health inspector to get to Kouris. The restaurant owner says he was rated "A," and Callen tells them that it's actually a "C." Sam acts like a customer who's upset at the inspection. Sam and Callen tell the owner to leave and approaches Kouris and fire fight breaks out.

Kouris says that he didn't kill Minas and it wasn't PK either. He tells the NCIS agents that if he was going to kill Minas he would have used a knife not explosives. Sam and Callen believe him. They head to the apartment Kouris mentioned.

Kensi finds the place the drone was built inside the garage. They don't understand why the killer would have killed a garage owner for the space. They find a large oven that was used to make a bigger drone. The small drone was a proof of concept. Minas was killed by his own concept.

The apartment Kouris followed Minas to leads NCIS to a new suspect, Rand Palmer. The drone was commissioned by a homegrown terrorist group against the government and corporations. They find Palmer's watch, which has GPS coordinates and NCIS finds the larger drone. 

NCIS races after the guy controlling the drone. The target is an oil refinery. The terrorist fire an automatic weapon and the agents. The car Kensi is driving gets a busted axel and they are out of the chase. Sam and Callen fire on the truck. Palmer runs off with the controller.

Callen takes out Palmer and has to try and bring the drone down in a safe location. Callen has trouble gaining control. He ends up bringing it down in the empty lot near them.

Afterwards, Sam wants to buy a drone with Callen, but Callen says he hates robots, even returned a Roomba. 

Hetty talks to Nell about her desire to be an undercover agent. Nell doesn't want to go the traditional route to become an agent. She's scared of going undercover because she can't do what the others do. She has to do them her own way even if that means she won't make it.

Hetty encourages Nell.