5. Nightmare of Eden
A surprisingly adult story based around drugs. The drug in question is Vraxoin which, according to the Doctor, has been known to bring down entire planets. We see its effects on a few characters, most notably a ships captain who completely loses all sense of responsibility and endangers a large number of lives. For such a serious story there is a lot of silliness but that was just the direction that the series was heading at the time. There's nothing in here any sillier than in the much-loved City of Death but with it being a darker tale, Nightmare suffers from the clashes of tone. There's nothing that can stop you from enjoying the four fantastic episodes though.