Fate has chosen this young man, the son of Space Patrol co-founder Gary Kinnison, to carry out a vital mission. The last surviving Lensman of the Boskone mission has his Lens transferred to Kim so that he may bring the lens to the Galactic Patrol and Admiral Haynes.

Having become a Lensman, Kim must learn about its abilities, such as its tendency to respond to his emotions and the ability to communicate to other Lensmen. Worsel, a fellow Lensman, helps him in this respect. There are other powers, however, that Kim must learn for himself. All the while, he has to use his cunning, courage, and feeling to save himself and his friends from the Boscone, ultimately pitting them against Lord Helmuth himself.