In the conclusion of the four-part story "Frontios," the super-intelligent insectoid Tractator race prepares to convert the planet Frontios into a huge space vessel. The Doctor (Peter Davison) must prevent this, lest he, his companions, and a group of survivors from a war-ravaged planet earth be completely wiped out. Complicating matters is the fact that the Tractators have commandeered the Doctor's TARDIS time-traveling vehicle. Originally telecast on February 3, 1984, "Frontios, Episode 4" was written by Christopher H. Bidmead. ~ Hal Erickson, Rovi