The narrative of this book is more complex than that of the previous Skylark books, and tells several stories simultaneously:
The Llurdi are a monstrous, purely logical race that enslaves humanoid races like the Jelmani. DuQuesne, given back his physical form, encounters them and begs Seaton and Crane for help. Simultaneously, the Llurdi experiment with freeing a group of Jelmani to see if the Jelmani can, while free, develop any interesting technology. They do and DuQuesne gets it from them. Meanwhile, Seaton and Crane discover that the Chlorans are a much more dangerous threat to the universe and set about discovering the technology to defeat them.
This book resembles the more famous Lensman books in its reliance on mental powers. Seaton and Crane refer to the saviors of humanity as "witches" from many worlds. However, the reader can think of this as more like the "Force" or Star Wars than the witchcraft of Macbeth.
" ‘Man is the ultimate creation of God.’ On Tellus it's ‘God created man in his own image.’ And of course the fact that I've never believed it — and I think it's unjustifiable racial self-glorification — does not invalidate it."