Jo peered through the panel and saw—nothing. Yet someone had entered the cabin. She could hear hoarse breathing and stealthy padding footsteps. A beaker rose in the air of its own accord, then dropped to the floor... The Invisible Enemy After pursuing the Daleks through Space, Doctor Who lands on the Planet of Spiridon, in the midst of a tropical jungle... and finds more than Daleks. Vicious plants spitting deadly poison, invisible Spiridons attacking from all sides and, in hiding, a vast army waits... for the moment to mobilise and conquer.