|Series||Roma Sub Rosa|
|Publisher||St. Martin's Press|
|Media type||Print (Hardback & Paperback)|
|Preceded by||Arms of Nemesis|
|Followed by||The Venus Throw|
Catilina's Riddle is a historical novel by American author Steven Saylor, first published by St. Martin's Press in 1993. It is the third book in his Roma Sub Rosa series of mystery novels set in the final decades of the Roman Republic. The main character is the Roman sleuth Gordianus the Finder.
The year is 63 BC, and Cicero is consul of Rome. Gordianus, once an associate of Cicero, has moved to the Etruscan countryside, where he has inherited a farm from an old aristocratic friend of his. Cicero, however, still needs his help, and asks Gordianus to look out for the notorious Lucius Sergius Catilina, who Cicero is convinced is plotting a conspiracy to take power in Rome. Then one day, Gordianus' daughter Diana finds a headless corpse in their stable, whom Gordianus dubs Nemo.