The four-part adventure "
The Visitation" begins as the Doctor (Peter Davison) attempts to take Tegan (Janet Fielding) back to contemporary London. Unfortunately, the TARDIS materializes in the London of 1666 at the height of the Great Plague. As if this wasn't enough to worry about, the Doctor discovers that an alien spacecraft may have landed in the disease-ridden city. Written by Eric Saward, Doctor Who: The Visitation, Episode 1 first aired on February 15, 1982. ~ Hal Erickson, All Movie Guide