This is the solemn saga of Tandra, a microbiologist from earth, who visits the moon base of two extraterrestrial species who have been viewing earth's ecological crisis with mounting alarm. The Ellls are amphibious, playful, emotionally oriented creatures; the Varoks look almost human but have inhuman self-control. This novel works endless variations on the psychic and sexual permutations possible between the human Tandra, the Elll Conn and the Varok Orram. Earth's a lost cause, but Tandra joins the brotherhood of beings. The Ellls, in particular, are appealingly drawn but the flashes of wonder get lost in high-minded long-windedness.