Jim Kirk is marooned on a strange planet that has a profound effect on humans. Carol and Jim's friends are puzzled by his disappearance and have to conduct an investigation to find him and whoever is responsible, while Jim is struggling to survive with his sanity intact on the strange world.

Spock gets transported back from a mission and a malfunction gives him amnesia. It slowly gets worse, eventually he can't remember where he is, who the crew are, who he is.