Tom Baker, Mary Tamm. The intergalactic hunt for the six segments of the all-powerful Key to Time takes place in "The Ribos Operation" (99 min.), "The Pirate Planet" (101 min.), "The Stones of Blood" (96 min.), "The Androids of Tara" (98 min.), "The Power of Kroll" (91 min.) and "The Armageddon Factor" (148 min.). 6 DVDs. 1981/color/NR/fullscreen.