"The Salmon of Doubt" was originally intended to be a Dirk Gently novel. The plot, set a few weeks after the events in "The Long Dark Tea-Time of the Soul", involves Dirk Gently refusing to help find the missing half of a cat, receiving large amounts of money from an unknown client, and then flying to the United States. Dirk pays a visit to Kate Schechter (who had first appeared in "The Long Dark Tea-Time of the Soul") and tells her that prior to the potential client, he had been so bored that he had started a habit of dialling his own phone number and discovered he'd answered his own calls.