The Head

In the middle of the winter, a small group of scientists in charge of an international base in the Antartica during the long polar nights stops communicating with the outside world.

A storm builds around the base and the search for Annika must be called off. Pressed by Johan, Maggie tries to remember what happened after Miles' death.

The surviving winterers are now certain that the killer was one of them. But who? And why? They need help. The Sno-Cats were their only chance to get close enough to the Argentinian station to call for help.

Arthur reveals that the body they found buried in the snow doesn't belong to any of the Polaris VI. It appears to be from a failed mission that ended in tragedy.

Back in Polaris V, the team did not find the radio parts they were looking for. But Maggie insisted to take the body found in the Polaris V back to Polaris VI.

Johan realises they've been searching in the wrong direction all along. He urgently redirects the search for his missing wife, which can resume after the storm has finally passed.

Far from land, Arthur Wilde and his team of scientists celebrate the culmination of decades of research: a solution to climate change. Then, a gruesome murder – eerily similar to Wilde's South Pole nightmare – occurs onboard.

Zach goes missing before he can release the DNA results from Kowalski's murder. Yuto brings Wilde the surprising results of his web search. Olivia escalates her search for the famous scientist.

With Charlie locked up, Amy brings lingering doubts to Wilde, confirming his greatest fears. In the U.K., Olivia and her sister are attacked while plotting their revenge.

After breaking out of his confinement, Charlie cuts the ship's power once again and embarks on a murderous rampage. As Olivia finds herself one step closer to Rachel, Gloria pulls away from Wilde.

After another scientist turns up dead, the mole reveals their true identity – and asks for a favor in return.

As the Alexandria threatens to explode, the remaining scientists jump ship and onto the only life boat – putting them face-to-face with the real killer.

In the lawless desert territory of Bir Tawil, a group of scientists carry out the next phase of Wilde's research: testing the bacteria on humans.

After a team member is stung by a scorpion, the others suspect sabotage on the base. Two years earlier, Arthur struggles to gain respect in prison.

Distrust mounts as the base's supplies continue to be tampered with. At Portlaoise, Arthur receives a letter from the anonymous admirer "XX."

The participants suddenly get sick just as the computers are infected with ransomware. Arthur does Patrick's dirty work in exchange for a cellphone.

After a forceful seizure of power, the subjects attempt to escape the facility. At Portlaoise, Arthur receives an unexpected visitor.

After Maggie helps Rachel successfully deliver her baby, the killer strikes again -- and XX's identity is revealed.