Dirk bills himself as a "holistic detective" who makes use of "the fundamental interconnectedness of all things" to solve the whole crime, and find the whole person. This involves running up large expense accounts and then claiming that every item (such as needing to go to a tropical beach in the Bahamas for three weeks) was, as a consequence of this "fundamental interconnectedness", actually a vital part of the investigation. Challenged on this point in the first novel, he claims that he cannot be considered to have ripped anybody off, because none of his clients have ever paid him. His office is supposed to be located at 33a Peckender St. N1 London. As an investigator whose cases often take a paranormal twist, he challenges the notion that – as presented by Sherlock Holmes – "when you have eliminated the impossible, whatever remains, however improbable, must be the truth", citing as an example an incident where a young girl is somehow reciting the stock market prices exactly as they change but twenty-four hours behind schedule. As Dirk describes it, it is impossible that the girl is getting those figures out of thin air, but the alternative implausible explanation is that the girl is masterminding a complex scheme with no obvious benefit to herself; the first idea suggests that something is happening that nobody knows about, but the second suggests a scenario contrary to typical human behavior that is known about.
Gently is psychic, though he refuses to believe in such things, insisting that he merely has a "depressingly accurate knack for making wild assumptions". The depressing part is that he is seemingly unable to use this knack to win money on horses. As a student at Cambridge University (St. Cedd's College) he attempted to acquire money by selling exam papers for the upcoming tests. His fellow undergraduates were convinced that he was psychic and had produced the papers under hypnosis, while he claimed he had simply studied previous papers and determined potential patterns in questions. However, when his papers turned out to be exactly the same as the real ones, to the very comma, he was arrested and sent to prison.
Douglas Adams was working on a third Dirk Gently novel, The Salmon of Doubt, at the time of his death. However Adams said "A lot of the stuff which was originally in The Salmon of Doubt really wasn't working," and that he had planned on "salvaging some of the ideas that I couldn't make work in a Dirk Gently framework and putting them in a Hitchhiker framework... and for old time's sake I may call it The Salmon of Doubt." The first ten chapters of this novel, assembled from various drafts following Adams' death, together with a memo suggesting further plot points, appear in The Salmon of Doubt: Hitchhiking the Galaxy One Last Time.