It's very easy to get a little disheartened when your planet has been blown up, the woman you love has vanished in a misunderstanding about the nature of space-time, the spaceship you are on crashes in flames on a remote and Bob-fearing planet and all you have to fall back on are a few simple sandwich-making skills. However, instead of being disheartened, Arthur Dent makes the terrible mistake of starting to enjoy life a bit and, immediately, all hell breaks loose.
Hell takes a number of forms: there is the usual Ford Prefect form of hell, fresh hell in the form of an all-new version of The Hitchhiker's Guide to the Galaxy which behaves in an altogether more mysterious, sinister and airborn manner, and a totally unexpected hell that arrives in the form of a teenage girl who utterly startles Arthur Dent by being his daughter when he didn't even know he had one.
Much as Arthur would love to stay in his rural sandwich-making idyll, he is forced to set off on his travels once again, this time on the back of a mysterious Perfectly Normal Beast. Can he save the Earth from total destruction throughout all dimensional probabilities? Can he save the Guide from a hostile alien takeover? Can he save the Grebulons from completely myopic junked-up idiocy? Can he save his daughter Random from herself?
Of course not. He never even works out what is going on, exactly.
Will you?
Mostly Harmless: The Hitchhiker's Guide to the Galaxy Part Five: The book that gives a whole new meaning to the world trilogy.