Illness and infirmity are as much a part of Potter's fiction as they were his life. Infirm characters had previously featured in his work (Moonlight on the Highway, Joe's Ark, Brimstone and Treacle) but Marlow was the first character to be bequeathed with Potter's own particular affliction, psoriasis. This of course caused speculation as to the autobiographical nature of the work, but as Potter says (in Potter on Potter), "rather than use an illness I knew nothing about, I used that particular one". Marlow's skin condition also serves as a metaphor for his psychological trauma, a physical manifestation of his childhood guilt. Marlow likens himself to "the leper in The Bible", the sins and poisons of the mind having manifested themselves on his skin. Peter Stead, in Dennis Potter, thinks it is related to his attitude to sex; "somehow his terrible infliction is a manifestation of his sexual disgust." It is perhaps notable that the night-club in the detective story, the sleazy hangout of prostitutes and a front for Nazi activity, is called 'Skinscapes'. Dr. Gibbons suggests the illness may be psychosomatic, so his psychological detective work is working towards curing Marlow's skin condition. Marlow is accused, by Gibbons, of using his illness as a retreat, "a cave in the rocks", Nicola, his wife, urges him to "come down from his tree" evoking the place young Philip hides from his father following his mother's suicide. It's possible he has retreated into illness rather than face his guilt. In Brimstone and Treacle (1976) it is an acceptance of Mr. Bate's guilt that 'cures' his daughter. It is significant that we see the first occurrence of the illness in the 10 year old Philip during one of Marlow's flashbacks (episode 5), his skin abnormality is first revealed after he has told his mother that he knows of her adultery.