In the conclusion of the four-part story "Arc of Infinity," the anti-matter creature that has bonded with the Doctor (Peter Davison) is revealed to be the notorious renegade Time Lord Omega (Ian Collier). Spared execution on his home planet Gallifrey, the Doctor pilots the TARDIS to earth for a final showdown with Omega. Unfortunately, this fateful confrontation may have dire consequences for the Doctor's companion, Tegan (Janet Fielding), who hasn't been seen since the 19th-season adventure "Time-Flight." First broadcast on January 10, 1983, "Arc of Infinity, Episode 3" was written by Johnny Byrne. ~ Hal Erickson, Rovi