Julius Cain was a replacement teacher on the school trip to Xirrinda. Realising that the Rain of Terror seemed quite valuable, Professor Willard and he captured and drugged three of the pebble creatures.
Julius had a plan to use a shuttle from their halfway stop to escape from the planet, but wasn't aware that the gravitational interference had a wide range. He took Amy hostage. They travelled into the sacred caves of the Ulla people.