Sorensen is brought aboard the rogue submarine. Ned wants to kill him, but his brother, Sean Ramsey, stops him.
The Nathan James attempts to locate the sub while not alerting it to their own presence.
Sorensen briefs the Ramseys on the Nathan James and her crew. They are confident that the can avoid detection.
Slattery interrogates the Spanish prisoner Juan Carlos from the Solace. He presents himself as unwillingly conscripted. He asks for asylum on the Nathan James. In Comms, the new sonar tech has detected the sub but can't get a bearing on it. They speculate that it is the British submarine Achilles. The submarine locates what they believe to be the Nathan James, and loads torpedoes.
The Nathan James and the Achilles feel each other out, and discuss each other's offensive capabilities.
Juan Carlos ties to convince Slattery that he has no loyalty Ramsey.
Chandler decides on a course that will hopefully give them some cover, while Slattery argues for a strong offensive move.
The crew bunkers down for "Quiet 2."
Ned is upset that they missed an opportunity to fire on the Nathan James. Sean predicts what Chandler is doing and adjust his own course.
The crew continues to shelter in place.
Sorensen goes over the inventory from the Solace, and Ned divulges the plan to sink the Nathan James and that Juan Carlos will act as a secret agent to secure the cure and other things that the Ramsey's are after.
Slattery tries to get more information out of Juan Carlos on deck. Juan Carlos starts bleeding from the mouth, he has activated a beacon for the sub, and discloses that the entire crew is immune, and that "they" have already taken Europe.
Juan Carlos is carried inside the helicopter bay, and Rachel performs surgery to remove the beacon.
Chandler and the comms team continue to attempt to track the sub, and he sends the helicopter out. He directs the ship into open water with a plan to mask their engine sounds as porpoises.
The crew of the Achilles argues over what to do. Ramsey decides to go active sonar which will alert the Nathan James to their position, but allow them to aim their torpedoes. The Nathan James takes evasive action and fires it's on torpedoes. The Achilles dives despite shallow waters. The Nathan James avoids being hit, but the Achilles has disappeared.
Mason is unsure if any of the Nathan James' torpedoes hit the Achilles. Chandler is reassuring.
The Achilles is scraping sea canyon walls, and the crew is on edge.
Rachel finds a flash drive in Juan Carlos, but no beacon.
Chandler and a crew member go over maps trying to figure out where Ramsey would go. Slattery delivers the flash drive to Alisha, but the data is corrupted.
Sorensen finds Dr. Hunter's name on some documents, and informs Ramsey that he knows where the Nathan James is ultimately headed.
The flash drive had the location of the CDC labs. Chandler and Slattery figure out that the Selected are after control of the cure. The Nathan James tracks missiles being fired at all of the CDC labs, and fires to intercept. They managed to only get two of the twenty six that the Achilles fired.
Rachel and Rios are unable to revive Juan Carlos for questioning.
Chandler Skypes with his kids and Kelly.
Rachel has figured out that the Selected are all naturally immune.
Sean Ramsey plans to conquer America like he did Europe.