The Impostors - S3.E17

Challenger, Roxton, and Marguerite take Finn to a cave where one year earlier a blinding light opened a doorway to another reality. Once inside, the explorers witness an eerie apparition of a man Finn recognizes and fears.

But when Finn races from the cave, the three figures who follow are not her friends-they're Kayle, Una, and Rixxel, three demons who have taken the place of Challenger, Roxton, and Marguerite. If the demons can remain on the Plateau for two days, they will permanently replace the explorers, and Kayle will be free to bring chaos and destruction to the world.

In the final deadly showdown between Finn and the demons, Finn must make the decision of her life-save the future or save her friends. Until an unexpected sacrifice changes everything…