In the third episode of the four-part story "Arc of Infinity," a renegade anti-matter creature (Ian Collier) has passed over into the normal universe by bonding with the Doctor (Peter Davison). The High Council of Gallifrey decrees that the only way to destroy the deadly creature is to execute the Doctor -- a fate to which he reluctantly but valiantly acquiesces. First broadcast on January 10, 1983, "Arc of Infinity, Episode 3" was written by Johnny Byrne. ~ Hal Erickson, All Movie Guide