An ethnologist for the human alliance "League of all Worlds", Gaverel Rocannon, arrives on a planet with medieval civilizations to study its peoples. Soon after, exploitative developers arrive, cutting him off from help. With the help of his newly-found allies, he makes a journey across continents to infiltrate their camps and use the their ansible to call secretly for help.

Absurdly large structures that would take a much more powerful civilization than ours to build, in addition to massive amounts of materials and energy.