This third book of the Gemini mission series focuses on the flight that simulated in Earth orbit the duration of an eight-day Apollo mission to the Moon. After the proof-of-concept test flights Gemini 1, 2 and 3 (as described in GEMINI FLIES!) and the success of the first American EVA as well as the four-day U.S. mission (GEMINI 4), NASA gained the confidence to gradually increase mission time spent in orbit. 
This is the first known book to focus solely on the Gemini 5 mission and its challenges with equipment failures and difficult living conditions. The mission was targeted to double the endurance of the previous one, and as such was an integral stepping stone for an even more audacious mission four months later. 
Attempting the eight- and then fourteen-day durations would be an opportunity for America to gain the lead in space exploration over the Soviets. This mission pioneered the duration of a flight to the Moon and back three years before Apollo 8 made that journey, without a lunar landing, for the first time.