A surprise assault on an Exploration Corps starship by implacably hostile, xenophobic aliens leaves its one remaining longboat as the only option for warning the home worlds of the existence of the predators. Unfortunately, the starship met disaster while thousands of light years from Earth. Theoretically, that sort of voyage in a longboat is possible but has never been attempted. In order to return, the crew has to stop on numerous unknown planets to renew supplies and hydrogen fuel many, many times along the way. They know they will certainly face danger and inimical life forms, as well as the hazards of braving interstellar space in a ship meant only for travel within a solar system. And before they get anywhere close to Earth they will need to figure out a way to destroy a much larger and much better armed alien starship. The ship shadowing their every move must not be allowed to follow them home to Earth and its colonies. The long journey has to succeed, even as more and more members of the crew fall prey to perils of the incredible journey. Humanity must be warned. There will be no second chance. Fail, and the poorly armed home worlds will likely die.