Dirk Gently's Holistic Detective Agency is a 1987 novel by Douglas Adams, the first in the Dirk Gently series.Dirk is a small-scale con artist whose latest scheme is working as a "Holistic Detective", who believes in the "fundamental interconnectedness of all things" and how that means that anything might prove useful in solving the whole cases of his clients — which, the way he sees it, means that he can do anything he likes, even take a three-week tropical vacation, and still charge it to the client as an expense. Of course, by Finagle's Law, somehow every mundane little job he starts off working on in each novel is somehow actually connected to the main plot, and he's the one who has to solve everything.In this novel, while (supposedly) investigating the disappearance of an old woman's cat, Dirk stumbles into a plot by an extraterrestrial ghost to undo his death with a Time Machine. Too bad that would undo the creation of life on Earth! (It all Makes Sense In Context. Even the robot created to be religiously faithful in place of its creators.)The novel started as a Recycled Script of Douglas Adams' Doctor Who story "Shada", which got stuck in Development Hell — several characters and locations are recycled from the episode wholesale. It also borrows heavily from Adams' Doctor Who story "City of Death".There is a second Dirk Gently novel, The Long Dark Tea-Time of the Soul.
Beware of Hitchhiking Ghosts: The driver of a car is horrified when he sees the ghost of his boss appear in front the car. The ghost, on the other hand, is horrified to see another ghost in the car's passenger seat.
Chekhov's Armoury: Dirk isn't wrong—everything that happens in these books is ultimately important. The Dirk Gently books embody this trope really because they are all about the interconnectedness of everything. Chekov's Armoury isn't just a device Adams used, it's what he based the whole book on. A poem, a conjuring trick, and a stuck couch in the first few chapters are all linked by the end.
Genre-Busting: DGHDA is described by its author as a "detective-ghost-horror-who dunnit-time travel-romantic-musical-comedy-epic".
Historical In-Joke: The novel ties together the origins of life on earth, Samuel Taylor Coleridge's epic poem "Kubla Khan", the extinction of the dodo, the career of Buxtehude, and dozens of other epochal or trivial events into an excellent approximation of a coherent plot.
Irrevocable Message: Which Richard attempts to revoke by breaking into his girlfriend's apartment (while possessed by a ghost). And he ultimately succeeds, for altogether more convoluted reasons ...
Laser-Guided Karma: Whatever Dirk claims to believe in order to extract cash from gullible people invariably turns out to really be true, but always in such a way that he looks bad, sometimes in such a way that he suffers physical or emotional trauma, and never in such a way that he gets the money.
Magicians Are Wizards: Reg performs an impossible magic trick to entertain a restless little girl at a formal dinner. Nobody but Dirk realizes that it's genuinely impossible, and he decides to investigate.
Dirk:You have a time machine and you use it for... watching television?
No Badge? No Problem!: Dirk does this as part of the workings of his Holistic Detective Agency when he has a mystery that actually interests him rather than one that involves tricking old ladies into letting their cats loose. The local inspector Sergeant Gilks takes a rather dim view of this... along with Dirk's tendencies to be involved in highly peculiar situations that Gilks does not like very much in the first place, as well as his habits of removing or obscuring evidence...
Not-So-Phony Psychic: When he was in university, Dirk posed as a psychic, was uncannily right, and got arrested for it. He now spends a lot of time insisting to people who were there that he's not psychic. Usually they don't believe him and his reputation often precedes him.
Perpetual Poverty: Dirk never seems to have much money — a Running Gag in Holistic Detective Agency is his secretary quitting over not getting paid — and most certainly never gets paid by his clients. He manages to stay in his office, flat, etc, through arranging the situation so that it would be more inconvenient to actually eject him or force him to pay than just let him be and hope that he'll pay some day.
Phone Call From The Dead: A guy makes a car phone call and starts talking into the answering machine, then gets killed. Just later his ghost tries to communicate by talking through the phone, which is recorded on the answering machine as well.
Religious Robot: The Electric Monks; a malfunctioning one ends up involved in the plot.
Ripple-Effect-Proof Memory: More prevalent here than usual; you have to lead a very sheltered life to never notice little discrepancies between your memories and reality.
Rubber-Band History: Samuel Taylor Coleridge finished writing "Kubla Khan" and nobody's ever heard of Johann Sebastian Bach's music. By the end of the novel, both of these have become our familiar versions of history. There's also a cautionary anecdote about inadvertant time travel resulting in the extinction of the dodo.
San Dimas Time: There's a telephone in the time machine, which can be used to straightforwardly communicate with the present. (On the other hand, there's a sequence where a character goes on a six-week trip into the past, and returns moments after he left.)
Schmuck Bait: Dirk told his fellow students he wasn't psychic, no matter how much money they offered him to predict the upcoming exam questions. Subverted, because he unintentionally predicted exactly what the questions would be.
Richard asks Dirk if he always carries a towel around.
Reg says that moving through time and space is closer than going to the chemist's—the opposite comparison that the Guide makes, "I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space, listen..."
Starfish Aliens: Living members of the alien race never appear, but the description in the opening scene reveals they have purple crinkly skin, a single eye but multiple mouths and noses, and a variable number of legs, but always a prime. The reason the Electric Monk looks exactly like a Caucasian human is so that no-one could possibly mistake it for a real person.
Suspiciously Specific Denial: Deliberately invoked by Dirk at university. By carefully denying the most extraordinary things, he convinces his fellow students that he's a psychic, mystic, telepathic, clairvoyant, psychosassic, vampire bat.