Mystery writers are authors who specialize in writing stories that involve suspense, crime, and intrigue. The four mystery writers mentioned in the crossword solutions are ANON (4 letters), POE (3 letters), CARR (4 letters), and SAYERS (6 letters). ANON is a pseudonym for an anonymous author, while POE is the pen name of Edgar Allan Poe, an American writer known for his gothic horror stories. CARR is the pen name of John Dickson Carr, an American-British author who wrote detective fiction. Lastly, SAYERS is the pen name of Dorothy L. Sayers, an English crime writer and poet.