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.