S3·E5 The Space Primevals

The primitive beings are actually wards of a computer, Protinius, which can confer temporary advanced sentience on the leading man in order to communicate Protinius' will.

The episode also features a temporary camaraderie between Don and Smith, a burying of the hatchet, when Don is rescued by Smith from a pit, and then says ""Doctor Smith"" - using the word Doctor for the first time unknown ages. However, their camaraderie dissolves and the characters are back to ""normal"". Not the first time Smith has become selfless and a man of some integrity, but as usual, Smith returns to normal.