The house introduced in the introduction is owned by Arthur Dent, who is a totally normal human being. That is, just like the rest of us, his house is in the way of a planned road that the local government wants to build.
In fact, Arthur starts off the day with a hangover, just like the rest of u…wait, what?, because he was down at the pub last night, drinking and complaining about how the local government wants to bulldoze his house.
Which explains why there are bulldozers outside his house right now.
So, Arthur goes out and lies down in front of a bulldozer. Pretty much your average Thursday.
The man in charge of the bulldozers is Mr. L. Prosser, who is a distant descendant of Genghis Khan.
Like Genghis Khan, Prosser has a bit of a belly and likes fur hats. Unlike Genghis Khan, Prosser is nervous and not so good at conquering.
Prosser tries to convince Arthur to let them destroy his house (just this once, pretty please), but Arthur refuses.
Arthur complains that the government did a terrible job of making their plans known. A letter would've been nice. Instead, Arthur had to go down to the local planning office, all the way to the cellar (even though the lights and the stairs were not working), and find the plans in "a locked filing cabinet stuck in a disused lavatory [bathroom] with a sign on the door saying 'Beware of the Leopard'" (40).
And the rest of the book is just the two of them arguing. No, that's not true. But before we hear what happens (do they fall in love? do they murder each other?), we get a long digression telling us all about Arthur's friend Ford Prefect.
We get a pretty in-depth description of Ford here, which is too bad if you are waiting to hear what happens to Arthur and Prosser. We'll just sum up the description by noting that "There was something very slightly odd about him, but it was difficult to say what it was" (1.56).
For instance, he makes fun of astrophysicists at parties he's not invited to, and sometimes he stares up at the night sky, looking for UFOs. See, he's slightly odd.
As the book explains, Ford is actually an alien, which was probably clearer to the British audience since "Ford Prefect" was a line of Ford cars around the 1940s-1960s over there—pretty cute cars, if you ask us.
Ford's actually a researcher for the Hitchhiker's Guide, but he's been stranded on Earth far too long. Who doesn't feel that way sometimes?
So, we move back to Arthur and Prosser, who are still stalemated regarding the relative importance of houses and bypass roads. Ford enters the scene.
Ford wants Arthur to go to the pub with to hear some amazing news. Arthur refuses to move because of the bulldozers, so Ford does the only logical thing: he gets Prosser to agree to lie in the mud in front of the bulldozer.
So, instead of bulldozing the house, Prosser is now in the position of preserving the house, making it possible for Arthur and Ford to the pub and get that stiff drink.
Arthur isn't sure they can trust Prosser, but Ford assures him they can trust him till the end of the Earth—that'll be about twelve minutes from now.