If The Mummy: Tomb of the Dragon Emperor demonstrates anything, it's that the pen is far mightier than the sword when it comes to killing off the undead. Well, an undead movie franchise anyway. No need for an archaeological dig to investigate what caused the collapse of this appalling ruin of a movie: every scene, every piece of banal dialogue and off-target one-liner points to the script penned by the writing team of Alfred Gough and Miles Millar.

Tomb of the Dragon Emperor picks up the story of the O’Connells in 1946, 13 years after the events of The Mummy Returns. We find Rick and Evelyn unhappily retired from a life of adventure, and their son, Alex, grown up and on an archaeological dig in China in search of the tomb of the Dragon Emperor, Qin. A ruthless and powerful ruler with a desire for immortality, Qin was cursed by a sorceress some 2000 years earlier, and turned to terracotta along with his entire army.

You’d have to think that if not for the O’Connells, being cursed probably wouldn’t be such a bad thing: as with the Mummy in the previous movies, if ever Qin is returned to life, he will become more powerful than ever and set about taking over the world. Ho hum, the old take over the world ploy rears its ugly head yet again. Cursing, it seems, is a bit like carbon emissions: the problem is simply shifted into the future when someone else has to deal with it. Fortunately the family O’Connell is on the job.

Tomb of the Dragon Emperor isn’t awful in the way of Highlander II or something equally horrific - a road accident for instance - both of which hold our attention through a mixture of horror and disbelief. It’s not even awful in the way of Indiana Jones and the Crystal Skull, which somehow manages to entertain in spite of itself. No, this third instalment in The Mummy franchise is just plain get-up-and-leave-the-cinema awful.

Like most sequels The Mummy Returns (2001) was a step or two down from its precursor, but nonetheless retained the light hearted humour of the first, along with the wonderful chemistry of Rick (Brendan Fraser) and Evy (Rachel Weisz). Stephen Sommers wrote and directed both, but chose not to be involved with the third except in the capacity of producer. The helm was given over to Rob Cohen (XXX, The Fast and the Furious) and to be fair, Cohen does action extremely well. The pacing of Tomb of the Dragon Emperor is fast and furious, the effects are impressive and it looks great (cinematographer Simon Duggan does a stunning job with the scenes set in China and the Himalayas, and the Yetis are a definite highpoint!). But Cohen is burdened with a script that hangs like a lead weight around his neck.

The other noticeable absence is Rachel Weisz. As late as September 2006 the Oscar winning actor was quoted as saying “I know there's a new script but I haven't read it yet. Nothing's definite yet and should the film be done, it’s probably going to happen next summer. And if so, I would definitely like to be in it.” So what happened? Speculation about why she pulled out was rife. Officially it was due to a scheduling conflict, or a desire to spend more time with husband Darren Aronofsky and their child.

My guess is she read the script.

Maria Bello bravely took on the impossible by replacing Weisz, and with predictable results. She does her best, but the lack of chemistry between the two leads isn’t helped by a script that bizarrely re-imagines her character. Giving it all a positive spin, she commented, “I think Rachel is so brilliant, and she was beautiful in that part, but they wrote my character so differently, I felt like it was a totally different woman. She has the same name, but she's quite a different character.”

Which is spot on. There’s only one question: Why?! What possible justification could there be for redefining a lead character who has an established history and identity? Bello’s Evy is frankly not the Evy whom Rick O’Connell married, or perhaps even would have married. She is barely recognisable as the Evy of the first two movies. This is not an issue of replacing one actor with another; it’s a question of continuity within the story itself.

Not only do the writers fail to understand the characters they inherited, they have failed to capture the tone or mood of the first two movies. They attempt to introduce dramatic tension and complexity to the relationships, particularly between Rick and Evy and Alex, but only succeed in introducing excruciating dialogue and a tone of seriousness that is completely out of sync with the fundamentally trivial nature of these movies. The one liners are simply not funny. John Hannah, playing Evy’s brother and providing much of the comedy in the first two movies, looks and sounds bored. Brendan Fraser’s wise-cracking Rick O’Connell misfires with such childishly sulky lines as “I hate mummies, they never play fair”, and so, for humour we’re left with a vomiting Yak!

I could go on, but enough is enough (although I will mention that there are in fact no mummies in this movie, despite the movie's title and an attempt to equate turning Qin and his warriors into terracotta with embalming). One final word though: it seems that killing off an undead movie franchise is as effective as cursing the Dragon Emperor because it looks like this undead movie franchise will rise again: a fourth movie is on the way: The Mummy: Rise of The Aztec (2010).

Can’t wait.