Star Trek: The Original Series, Series 3, Episode 14. First broadcast on Friday 3 January 1969.

A Very Important episode of Star Trek: The Original Series this week, in which we tackle the Serious Issue of Mental Illness, a Terrifying Social Problem which causes ordinary people to conceive an Unquenchable Desire to Take over the Entire Galaxy and to Use Capital Letters Unnecessarily. Fortunately, it can be cured by a Simple Intravenous Injection, which seems to have started working almost immediately. So, no harm done really. Except to this episode’s guest woman, who is dead.