The serial marked the last regular appearance of K9 in the classic Doctor Who series, though he would reappear in the spin-off K-9 and Company: A Girl's Best Friend (1981) and also in the 20th Anniversary special The Five Doctors (1983). K9 would reappear in the new Doctor Who series in the episode "School Reunion" in 2006.
The mood on set was tense: Tom Baker and Lalla Ward, who had previously renewed their romantic relationship, were fighting (with Ward's imminent departure from the series not helping matters), and both were deeply unhappy with their dialogue. Paul Joyce recalled - "I don't think even Tom Stoppard or Harold Pinter could have written a scene that would have satisfied both Tom and Lalla at that point."
Kenneth Cope has stated in interviews that he thought this was the best script he had acted in for 10 years.
On the DVD featurrete "The Dreaming" Clifford Rose and John Leeson say in interviews they were baffled by the serial.