 The book is a collection of most of de Camp's early ""Viagens Interplanetarias"" tales, all of which are set in a future in which interstellar travel between the Solar System and nearby stellar systems inhabited by alien races is common, and an Interplanetary Council regulates relations between the various civilizations.Terrans and the reptilian natives of the planet Osiris are the main spacefaring peoples.The tales take place in the period from the mid-21st-century to the mid-twenty-second.