Set in 2058, the third planet of the Ypserlon system, Clayad, lies 43 light‑years from Earth and is suddenly raided by alien forces. The emigrants must escape, but amid the chaos several children become separated from their parents and are taken aboard the training spacecraft Janous. After many sacrifices, the group reaches the fourth planet, Belwick. However, Belwick is already embroiled in war, so the thirteen children must make the journey to Earth on their own.