The show opens up with a meeting in a Russian restaurant between Russian Counselor Anton Pavlenko and an international mercenary by the name of Sergei Mishnev.
The two don't like each other very much, and Pavlenko warns Mishnev not to attack NCIS. Mishnev goes through a pile of photos of the NCIS team and tells him there's no business involved, that his hunt for them is personal.
Meanwhile, Gibbs and McGee are assigned to go to Moscow and escort system admin Kevin Hussein from the American embassy to safety at home. He has a lot of valuable information, and has been paranoid that someone had been following him in Russia. They exit the embassy via helicopter.
On the way to the ship, they are shot down via surface-to-air missile, landing about twelve miles - or "twenty klicks" - from the border of Finland. A helicopter technician is killed in the crash, and the pilot is severely injured.
While they are trying to figure out how to get a radio working, a mercenary team led by Mishnev shows up. The team, except for the injured pilot, hides, while the mercenaries are offered some misdirection.
All but one of the mercenaries go hunting for the NCIS team. The lone one comes back and, when it looks as though he's going to attack the injured pilot, Gibbs comes up from behind and stabs him to death.
Gibbs determines that Hussein - the man they were rescuing - is hiding a secret. It turns out that Hussein had been approached by Mishnev and was asked to provide a supervirus weapon to him. Before the deal was concluded, Hussein had backed out, and so Mishnev began to hunt for him. Hussein hid the micro-SD weapon containing the virus on the body of his father, who had been shot dead by Mishnev. He had then arranged for the body to be shipped back to America.
Meanwhile, McGee had rigged the dead mercenary's radio so that he could call back to NCIS headquarters. Just as he was providing their location coordinates to Vance, one of the mercenaries begins shooting, and injures Hussein in the leg. Gibbs gets out a sniper rifle and kills one more of the attackers, after which the team escapes yet again.
Gibbs and McGee set up a campfire, which Gibbs uses to heat up a knife, so as to cauterize Hussein's leg wound. They then ensure the fire keeps going, hoping to use it as bait to bring out their attackers.
The bait works, and while the attackers shoot toward the fire, Gibbs destroys their vehicle with a grenade.
As they struggle to escape to the border of Finland, Gibbs tells McGee and Hussein to move on ahead, while he hangs back to slow their attackers down. Gibbs kills two more of the mercenaries, leaving only Mishnev.
Tony, having received their coordinates, finally shows up in a vehicle to get them across the border. Just then, Mishnev shows up, and Gibbs shoots him. He has no time to check his body however.
Gibbs in his basement at home when Vance comes calling, to let him know that Mishnev is alive and that the whole scenario was an elaborate setup to "get back" at NCIS.