This is Sylvester McCoy's favorite serial of the twelve he starred in. However, he has admitted that he didn't understand it. He was quoted: "It was well done but God knows what it meant."
Many of the cast have gone on record saying they never fully understood what they were doing. Neither did the director.
The working script was heavily edited, with a number of explanatory scenes ultimately being omitted. The result is a plot that, unusually for Doctor Who (1963), generally needs to be viewed several times to be understood (and some reviewers have argued even that isn't enough to work it out). Even the cast and crew were confused by it. Patrick Mulkern wrote in the Radio Times that the story was "a shambles... as a piece of television drama it is incoherent and almost incomprehensible. The incoherence is ultimately Andrew Cartmel's responsibility. As script editor, it was his job to hone these scripts into three 25-minute episodes of prime-time drama."
The story evolved out of an earlier, rejected script entitled Lungbarrow. It was to be set on Gallifrey in the Doctor's ancestral home and deal with the Doctor's past, but John Nathan-Turner felt that it revealed too much of the Doctor's origins. It was reworked to make both evolution and the idea of an ancient house central to the story. Marc Platt described the original version as "The Addams Family (1964) on acid".