It seems like The Ghastly Ordeal of Timothy Cavendish starts with Dermot Hoggins, the author of Knuckle Sandwich, "a well-written, gutsy fictional memoir" (4.1.50). After Dermot throws book critic Felix Finch off a balcony at a party, Knuckle Sandwich's sales skyrocket, and Cavendish, Hoggins's publisher, is the one who profits. When Dermot's bros—Eddie, Mozza, and Jarvis—tell Cavendish they want fifty thousand pounds, Cavendish goes on the run.
This is the start of Cavendish's story, but it's not the start of his problems. His problems started when he decided to capitalize off of another person's work. He took Hoggins's money, printed his book, and then did absolutely nothing with it. He admits that Knuckle Sandwich "was yet to enter a bookshop" (4.1.14). And he's so vehement in his denial that he invited Hoggins to the same party as Felix Finch that it makes us wonder if he did, in fact, do it, maybe to stir up some negative publicity.
Sure, Dermot and his brothers are a few crustless cucumber sandwiches short of a tea party, and no one deserves to be thrown off a balcony to his death, but we can understand why they're angry.