Junior diplomat in humanity's legation to the Intergalactic Exchange outwits aliens bent on enslaving all humans. Yake Singh Browne, Assistant Liaison officer with the 113th Interstellar mission, is told by the ever-so-polite Drooughleem representative--a 13-foot-long slug--that mankind is overdrawn at the memory bank, and may have to pay for the torrent of galactic information they've been ingesting for many years by offering live humans as breeding grounds for one or more of the predominantly insectile races that inhabit the galaxy. Browne suspects that they've been conned--a suspicion confirmed by the Dragon, a member of the Council who offers not to have Browne for lunch if he proves sufficiently interesting. Browne and his associates discover that the Drooughleem are indeed cheats; in the process they pay off part of their debt by discovering that the Ki!, large praying mantises, have illegally enslaved a lost human colony and are using its people to kill off the Fn-rr, intelligent trees who share a world with the Ki! This is third in the Millenium series, built around major science-fiction themes. The theme in this case is classic space opera, with roots in Flash Gordon (a comparison heightened by drawings patterned after early comic strips). The story, however, is taut and well-constructed, providing a convincing glimpse of alien biology and psychology. ""In the tradition,"" say the publishers, ""of Douglas Adams and Piers Anthony."" Well, no, more early L. Ron Hubbard; but a good yarn.