The Time Lords send the Doctor to a sky base circling the planet Solos, bearing a box that will only open for its intended recipient. The planet's colonial Administrator is about to grant the inhabitants their independence when the Sky Base's Marshal, determined to maintain and consolidate his authority, has the Administrator assassinated. The Marshal and his scientific advisor, Jaeger, intend to make the planet habitable only by Earth natives. The Solonions are mutating into large, insectlike creatures, but no one knows why. Are Jaeger's experiments to blame, or is it something else? The answer may lie in the box the Doctor carries-if he and a scientist named Sondergaard can translate the hieroglyphs in time.