The inventor Samaon Gai from the planet Wester, with the help of his daughter Iriya, built an intelligent starship Gai-do. After Samaon’s death, Iriya Gai—raised as a scientist and a fearless fighter—refuses offers to build a new ship and conducts research flights with Gai-do. On the uninhabited, inhospitable planet 5-4, she finds a dying Earthman, Tadeusz. Near the crash site, Gai-do discovers an entrance to a mysterious base of travelers who, as is known, rose to a height unprecedented for Earthlings—but disappeared a hundred thousand years ago. Iriya categorically refuses to investigate the base and takes Tadeusz back to his homeworld Wester, and then to Earth so he can recover in his native climate. Under the influence of the love that flares up, her values are reassessed: she is happy with Tadeusz and doesn’t intend to fly into space anymore. Meanwhile, Gai-do serves as a tender on a geological expedition.