An unknown piece of space junk plows into the atmosphere of Venus, witnessed by the manned station Fort Bliss in orbit. It survives and impacts the ground, near a base jointly operated by UNISPACE and the Russians. The object turns out to be a Keeper unit, arrived from alien origins deeper in the solar system. Above them coursing through the atmosphere, a manned airship is damaged by the object's descent and the crew has to be rescued.
Colonel Johnny Winger and a detachment of quantum troopers are sent to find out what has landed on Venus and why the base has been silent for weeks. They soon find themselves incarcerated by the Russians at Ishtar Base, for the Russians and their cartel cronies are trying to plumb the secrets of the fallen Keeper and make use of its technology for their own ends, in violation of all treaties.
With help from his fellow troopers, Winger manages to accompany an exploratory expedition out to the Keeper but conditions on the surface make it impossible to hold his configuration and Winger must hide in a nearby cave to save himself.
Still incarcerated inside Ishtar base, the detachment devises a ruse to escape and subdue their Russian captors. Leaving three behind to gather intelligence, three remaining crewmen then head out in a crawler vehicle to rescue Winger, but they are assaulted by something no one expected...flocks of huge, extremophile birds, dubbed thermosaurs by one of the crew, and have to seek shelter. They locate Winger but with their vehicle damaged and surface conditions of Venus so dangerous, they are trapped.
Only a harrowing flight by the detachment lander to the Keeper site and last-second heroics by crewman Emily Blakely to draw off the attacking thermosaurs, allows the lander to set down. Armed with critical intelligence on the Russian base and what they are harboring, the quantum troopers have to find a way to lift off through the thick atmosphere and avoid the swarming 'saurs while avoiding the quantum effects of the nearby Keeper.
Fifth episode in the Quantum Troopers Return serial.