"Return to Tomorrow" is the twentieth episode of the second season of the American science fiction television series Star Trek. Written by John T. Dugan (under the pen-name "John Kingsbridge") and directed by Ralph Senensky, it was first broadcast February 9, 1968. In the episode, telepathic aliens take control of Captain Kirk, Dr. Ann Mulhall (Diana Muldaur), and First Officer Spock's bodies in order to construct android hosts. This episode was the first appearance of Diana Muldaur in the Star Trek franchise. She appeared again as Dr. Miranda Jones in the third season episode, "Is There in Truth No Beauty?" and as Dr. Katherine Pulaski in the second season of Star Trek: The Next Generation. Plot The starship Enterprise receives a distress call from a lifeless planet. Upon arrival, a telepathic being named Sargon (voiced by James Doohan) addresses Kirk and Spock as his "children", and invites them to beam down to the planet. Kirk, Spock, Dr. McCoy, and Lt. Cmdr. Ann Mulhall beam to a subterranean vault where the voice of Sargon greets them from a luminous sphere on a pedestal. Sargon explains that he and two others are the last survivors of their race; their minds, stored in these spheres, have existed here since their planet was devastated by war. Sargon then transfers his mind into Kirk's body and Kirk's mind into the sphere. Sargon explains that he and his companions will need human bodies temporarily, in order to construct android hosts for themselves, and then returns to his orb. Kirk, returned to his own body, declares his confidence in Sargon. Back onboard the Enterprise, the four meet with Chief Engineer Scott to consider Sargon's request, and Kirk convinces the others with a rousing speech about risk. The spheres of Sargon, his wife Thalassa, and his former enemy Henoch, are brought up from the planet. McCoy supervises as Sargon takes Kirk's body again, and Thalassa and Henoch take Mulhall's and Spock's bodies, respectively. When Sargon and Thalassa become exhausted by the strain of the transference, Henoch instructs Nurse Chapel in preparing a serum that will strengthen the host bodies. Chapel notices that the serum in the hypospray designated for Kirk does not contain the correct formula. Henoch confesses that he intends to kill Kirk, and Sargon with him, in order to keep Spock's body. Henoch then erases Chapel's memory of the conversation. Manufacture of the android hosts begins.