The novel “The Secret of Sinharat” by Leigh Brackett was published for the first time in 1964 and is a revised and expanded version of a 1949 novella titled “Queen of the Martian Catacombs”

Eric John Stark fled to Mars, where he offers his services as a mercenary. He’s found by the Earth agent Simon Ashton, who forces him to act as an informer for him to avoid being arrested for crimes committed on Venus. Stark must infiltrate a group of barbarian leaders who are setting up a war.