And so it comes down to what you always knew it would--blood. There has never been a story so raw as the first four episodes of Doctor Who; the danger has never seemed so real, the violence so intense, the brutality so shocking. The opening sequence, where the Doctor tricks Kal into revealing his betrayal of the tribe, is such a cunning piece of wit that in a lesser-but-still-good series, it could have stood as the conclusion. "There is no blood on this knife," the Doctor says, and Kal, knowing he has lost the advantage, bluffs that "it is a bad knife. It does not show the things it does." Again, note how clearly this is portrayed as a trial. The tribe understands the points being made. They're following the discussion with riveted intensity. These are not stupid people. So many times, science-fiction (even Doctor Who itself) portrays primitive cultures as "like us, only dumb and superstitious". These people are portrayed as "like us, only without the pretense that we're not like them".
What follows, as Kal is driven away only to return with murder in his heart, has to be one of the best-directed sequences in the series' history. The fight itself should be nothing special. It's two men in silly costumes wrestling. But Waris Hussein captures the bloodlust on both sides perfectly. It's absolutely clear from the moment the fight starts that it's only going to end when one of the two is dead. The final sequence, where Za picks up the rock and shatters Kal's skull with it, is utterly chilling even without seeing any blood. I really can't imagine this looking any better in 2005.
After that, Za, whose life was saved by Ian...surely he'll understand the lessons of friendship and trust? Why, of course he does! He understands them so well that he's willing to offer the group a lifelong alliance, a place in his tribe not offered lightly. After all, none of them can hunt. Their leader is old and feeble. The last person he accepted into the tribe tried to usurp him, and the one before that has spent most of the story undermining his leadership. Za's offer is a political alliance, and a very intelligent one at that.
Until finally the TARDIS crew gets their chance and legs it. This is a bit of a weakness, the only time when the tribe acts stupid and superstitious the way cavemen are expected to. But even then, we see Za pointing out the obvious--it's just a bunch of torches with skulls on them, people! Pull it together! And then there's time for just one last chase into the TARDIS, a frantic flight to safety that again manages to transcend its budgetary limitations by playing the tension absolutely straight. I won't say it couldn't have looked better in 2005, but it could never have been done in the new series. You could never imagine Rose and Tennant, or Smith and Coleman, staggering into the TARDIS in a state of bruised, battered, bedraggled exhaustion. Time travel is never going to be this scary again in Doctor Who, mainly because you'd wonder why they ever left the TARDIS if it was, but it's damned impressive here.
In a lot of ways, this is still only the beginning--it could be argued that the first story is 77 episodes long, and is the tale of Ian and Barbara's wild adventures through time and space--but it's an amazing beginning. It's still worth watching for its own sake, and not just as a piece of history. And that's pretty awesome for a fifty-year old piece of television.