Star Trek: Season 2, Episode 9

2 - 9: Metamorphosis

Enterprise sends a shuttlecraft to retrieve Federation Commissioner Nancy Hedford, who suffers from Sakuro's Disease, so that she may be treated. The craft is pulled off course and lands on a small planetoid, where the crew discover the systems will not work. They also discover a man, apparently living alone there - or, is he? He seems to from time to time commune with an energy cloud, the alien being responsible for forcing the shuttlecraft down. It means for the crew to serve as companions for the man - forever.