"Laddie..." - While retrieving and repairing a remote-controlled space rover, Montgomery Scott finds a different kind of rover- an Earth terrier abandoned on the planet, which seems odd, as no manned ships have made it out this far. Feeling sorry for it, he decides to adopt the poor animal. However, as usual, strange things start to happen; Spock develops severe headaches and goes into a telepathic coma, the ship's controls go haywire, and it's steering straight for a dangerous area of space. The "dog" is in fact a member of a species that lives in the inhabitable reason, but got lost, and it's trying to fly its way back home. It didn't mean to hurt them. When they get back to the other "dogs", Kirk needs to ask them to help Spock. Scotty, meanwhile, bids a sad goodbye to his little friend.
Next episode: "The Gardens of Friora"
Next episode: "The Gardens of Friora"