David Starr, Space Ranger, is set around A.D. 7,000 (five thousand years after the first nuclear bomb, as stated at the beginning), when humanity has founded colonies on the inner planets of the Solar System, as well as spreading to other planetary systems with separate and sometimes hostile governments. The most powerful organization in the Solar System is the Council of Science, which uses scientific expertise and intrepid field agents to counter political and military threats to Earth's government.

Protagonist David Starr is a young biophysicist orphaned as an infant and raised by his guardians, Augustus Henree and Hector Conway, high-ranking Council members who send David on his missions for the Council. They tell him of some 200 recent victims fatally poisoned by produce imported from Mars. Fearing a conspiracy to start a food panic and wreck interplanetary trade, they send Starr undercover to Mars.