The episode was a heavily rewritten version of an earlier script called The Invaders. The first half was largely unchanged but the original script had the Liberator travelling through a fluid cloud (similar to the one later seen in "Terminal") and a lifeform that only Gan can see coming aboard the ship. The lifeform ended up taking on Gan's form and Blake and Gan teamed up to force it into the teleport chamber and teleport it off the ship. The visit to the station formed a much smaller part of the narrative, with the staff merely performing the operation and giving the Liberator time to get away before informing the Federation.
The original title was Brain Storm.
Douglas Camfield, who had previously directed Duel (1978), was asked to direct this episode. He declined, as he was busy with other TV work.
Julian Glover, who played Professor Kayn, is married to Isla Blair who played Sinofar in Duel (1978).