Scooby Doo 2 (PG)

Scooby Doo 2: Monsters Unleashed starts with the gang from Mystery Inc basking in the glory of their past crime-solving exploits.

The five sleuths turn up for the gala opening of a museum exhibit chronicling their detective skills, but things soon turn sour when a ghost (not just a masked man this time) runs amok.

It's clear that the Mystery Inc gang is being set up and that they will need to act quickly to save their reputation. Zoinks! Freddie, Daphne, Velma, Shaggy and Scooby have to use all their skills to get to the bottom of things.

As with the first movie, the real stars are Matthew Lilliard's spot-on Shaggy and the computer-generated pooch.

The pair provide the only real warmth in the movie and the '70s-inspired disco scene is genuinely laugh-out-loud funny.

If only the script was as tight as Scooby's purple jumpsuit and the plot had as much bounce as his Afro wig. The rest of the cast - Sarah Michelle Gellar, Freddie Prinze Jnr and Linda Cardellini - is also poor value for money. It may be based on a cartoon but is that any reason to put in two-dimensional performances?

The plot twists and turns without throwing up any real surprises, and, for younger fans, it could just be plain confusing.

Scooby Doo 2 moves along quite nicely for the first hour despite the wafer-thin story. This is largely - no, entirely - down to the Shaggy and Scooby double act.

Once the writers try to move away from these two and start to think about how to end the movie, things go badly wrong.

In fact, the more they think about the plot, the more they look like they have lost the plot.

Director Raja Gosnell, who was also at the helm for the original, resorts to special effects to carry the film to its climax when the villain's clever disguise is removed.

The final third is a tortuous half-hour of screaming CGI banshees and the inevitable unmasking is a relief, if not a surprise.