Arman reluctantly embarks on a submarine research trip sponsored by his father. At the Incirlik Air Base, Hatice reports an unusual radiometer reading.

Amid a search for survivors in Kos, Arman and Defne rush to find Kenan before sunrise. Felix and Cem scramble to restore electric power to the town.

Inside the submarine, tensions come to a head between Arman and Umut. When Barış's actions unravel, Erenay confronts an impossible dilemma.

Arman and Yonca must swim out to fix a rupture, but the submarine is still in jeopardy. The Yakamoz crew discovers an intruder.

After Hatice reveals a shocking truth about Erenay, Umut and Yonca begin to suspect Defne. The crew tracks an airplane. Cem makes a devastating choice.

Umut decides to switch course and head for a seed vault in Norway. Hatice snoops inside Defne's room. The crew docks in Spain, and carnage ensues.

Umut reads a message from NATO that leads him to lash out against Arman. Arman sets a trap for Umut and speaks to his father on the phone.