The Doctor arrives on a distant world populated by two tribes, the Sevateem and the Tesh. He quickly bumps into a Sevateem woman named Leela, who has been banished from her village for denying the existence of Xoanon – an entity whom the Sevateem worship as a god. The Doctor can only stand by helplessly as the Sevateem mount a suicidal attack upon the more advanced Tesh. The Doctor soon realizes that these primitives are the descendants of an interstellar exploration detail: the survey team and the technicians. Both tribes recognize and revere him as the Evil One…but despite the bloodshed, no one will allow him to go near Xoanon, a sentient computer whose tyrannical rule is a result of the Doctor’s past interference.
written by Chris Boucher
directed by Pennant Roberts
music by Dudley SimpsonGuest Cast: Leslie Schofield (Calib), Victor Lucas (Andor), Brendan Price (Tomas), Colin Thomas (Sole), David Garfield (Neeva), Lloyd McGuire (Lugo), Tom Kelly, Brett Forrest (Guards), Leon Eagles (Jabel), Mike Elles (Gentek), Peter Baldock (Acolyte), Tom Baker, Rob Edwards, Pamela Salem, Anthony Frieze, Roy Herrick (voices of Xoanon)
Original title: The Day God Went Mad
Broadcast from January 1 through 22, 1977
LogBook entry & review by Earl Green
Review: After seeing this pivotal adventure – pivotal because it introduced the wildly popular Leela to the series – for the first time in over ten years, I have to say that it’s better than I remember. In some ways, the basic premise of a primitive society evolved from the remnants of a much more advanced, and yet doomed, civilization is almost Roddenberryesque. Similarly, I think Gene would’ve approved of the plot point of questioning one’s deities. It’s actually a very Trekkish story overall (for Doctor Who). In Who-ish terms, though, the insane computer is a very old plot device – utilized by stories as old as 1966’s The War Machines and as recent (for this 1977 adventure) as Jon Pertwee’s 1973 battle with The Green Death. The Face Of Evil is set apart by the Doctor’s direct responsibility for Xoanon’s 
insanity – a plot twist worthy of the late 80s’ painted-heavily-in-shades-of-grey seventh Doctor adventures. Tom Baker gets to exercise some real acting muscle here – not only as the Doctor, but as Xoanon.
One sometimes inconsistent feature of this four-parter is the Doctor’s stance on violence. One moment, he deplores Leela’s habit of fatally felling any foe who crosses her path – and the next, he’s holding two of her tribesmen at gunpoint with a crossbow as he tries to find an antidote to the janis thorn, the Sevateem’s usually-deadly weapon of choice. (In the latter scene, he also threatens to break somebody’s nose.) It’s a worthwhile message, but also a muddled message. Leela herself actually gets a very good introduction, one which later stories betray by playing her as a simple savage. In this story, she knows enough to question whether or not Xoanon is a god, which is a sign of an intelligent skeptic, not a barbarian.
Produced one year before the first season of Blake’s 7, The Face Of Evil is peppered with future Blake veterans – writer Chris Boucher became the script editor overseeing Blake’s 7, while Leslie Schofield and Tom Kelly each had early major guest roles in that show’s first season, and Pennant Roberts directed numerous early episodes.