Doctor Who: The Hand Of Fear (1976)

Quarries are a bit of cliché in Doctor Who, as an easy shortcut to represent an alien planet, but The Hand Of Fear subverts that by having the TARDIS materialise in an actual quarry on Earth - and Sarah Jane Smith initially doesn't believe they are back on her home world!

An explosion goes off in the quarry catching Sarah Jane and The Fourth Doctor in its wake. Sarah Jane has to be dug out from under a rock fall... and she is holding on tightly to a 150 million-year-old fossilised hand.

The hand once belonged to an silicon-based lifeform, from the planet Kastria, called Eldrad.

The creature brainwashes Sarah Jane to take it to the nearby nuclear power plant, where it absorbs vast quantities of radiation to regenerate itself a body - a strangely attractive female form played by Judith Paris.

To prevent Eldrad wreaking any more havoc on Earth, The Doctor agrees to take her back to her home planet - not back to the time she left, as she asks, but as it is now.

The Hand Of Fear is a very simple, straight-forward story with a beautifully poetic Twilight Zone-like twist that is almost Shakespearean in its tragic inevitability.

In its female form, Eldred is quite an intriguing entity, shifting our perceptions from suspected traditional, tunnel-visioned world-conqueror stereotype to hard-done-by victim just looking for a way home. It's only when she later changes into her male form that Eldred becomes the one-dimensional, megalomaniac that we originally thought the character was.

Set for the most part on modern day (ie 1970s) Earth, around the Nunton experimental nuclear complex, this story has inescapable Third Doctor overtones, with a dash of contemporary thriller thrown in for good measure.

I wonder if UNIT was alerted to the problem - especially as the plant's head Professor Watson (Glyn Houston) likes to try and resolve issues by employing firearms and tactical nuclear strikes (you have to question the logic of bombing a creature that thrives on nuclear radiation with a nuclear missle!)

But then there are a lot of "liberties" (to put it euphemistically) taken with science in this story anyway (the general attitude to impending nuclear explosions seems to be if you just hide round a corner and cover your eyes you'll be okay).

In this, her last Classic story as a regular companion, Sarah Jane is certainly put through the wringer - buried under rocks, hypnotised, exposed to deadly radiation and freezing cold temperatures, and nearly toppled down a bottomless chasm.

Her farewell scene with The Doctor - who has been summoned to Gallifrey (for The Deadly Assassin, his one companionless Classic adventure) - is wonderfully played and quite emotional.

Now, of course, we know she would remain a core element of the Whoniverse, returning in The Five Doctors and K-9 And Company, then in the new Who with the 10th Doctor, and finally in her own series, The Sarah Jane Adventures.

While she will always remain one of his most beautiful and brainy assistants, Sarah Jane's Achilles' heel was her fashion sense - as ably demonstrated in this story where she sports a particularly striking set of pink-striped, Andy Pandy-style overalls.

Thankfully, by the 21st Century, and the Sarah Jane Adventures, her experimental fashion phase appears to be behind her.