Night at the Museum: Secret of the Tomb (PG, 98 mins)

Director: Shawn Levy

3 stars

Talk about stretching an idea so thin you can start to see through it. The premise of the first Night at the Museum movie eight years ago was that a magical tablet could bring the exhibits of a New York museum to life at night, which was realised through what at the time were fairly nifty computer generated effects.

Ben Stiller was Larry, the night security guard at the museum who got caught up in the middle of the mayhem when dinosaur skeletons and Attila the Hun starting running amok. Now Larry is in charge of putting on a show for dignitaries, who think the animated exhibits are special effects.

Before we get to that there's a prologue set in 1930s Egypt that gives us a bit of half-hearted background on the tablet, as some Indiana Jones-style tomb raiders disturb it amid the standard warnings of a curse.

For reasons never explained this curse involved absolutely nothing happening for nearly 80 years, but now the tablet is corroding and the exhibits are going screwy. The solution, invented by the film's writers for no reason other than it would be nice to go to London, is that they must go to the British Museum to try to free the curse.

Or something. Because none of it follows a remotely logical or coherent path, and there's really very little to it in terms of threat or excitement. The situation is paper-thin, the jokes are lame and the special effects aren't even particularly special. It looks pretty horrible too, the direction is lacklustre and it seems scaled down from previous instalments.

There's the need for some uninspired padding involving Larry's teenage son, and whether he will or won't go to college. Another exciting subplot to look out for in the fourth film; will Larry do the dishes or leave them until the morning?

Yet for some reason it's perfectly watchable and affable, mostly thanks to a game cast, and mostly thanks to Dan Stevens. He pops up as Sir Lancelot and has some fun with the action shenanigans while also demonstrating a nice way with comic timing as he fails to understand anything going on around him.

We also get the final acting appearance of Robin Williams, who reprises his role as Theodore Roosevelt. It's hardly a fitting send-off, with he and just about every character other than Larry and Lance given insufficient material to make any impression.

In the end this is unlikely to be remembered as one of the great trilogies. Really it barely passes muster, and in a few years there might not even be many people who remember it was a trilogy at all.

But it rattles along quickly and it's never dull, which actually counts for something. And if it looks like it's only scraping a third star by the skin of its teeth, which it is, that's because it's Christmas, and it's because we get to see Dick Van Dyke dance.

Director: Shawn Levy

Running time: 98 mins

Dumb and Dumber To (15, 109 mins)

Directors: Peter Farrelly, Bobby Farrelly

1 star

There's no inherent difficulty with bringing back the characters of a well-liked movie 20 years down the line, but if the results are as weak as this then questions need to be asked.

Dumb and Dumber introduced us to probably the most dim-witted characters ever put on film, Harry and Lloyd (Jeff Daniels and Jim Carrey), who got into all sorts of good-natured if sometimes disgusting scrapes.

Now they're back and Harry is in need of a kidney transplant, which involves the two of them taking a road trip to find the daughter Harry didn't know he had. Rather than crafting well-thought out set-pieces, this is a comedy absolutely obsessed with bodily functions, packing in as many gross-out gags as possible but never managing to make them work in the way that something like The Inbetweeners does.

The truly galling thing is that the jokes are in there somewhere, but they're botched in execution and timing, resulting in a black hole where the laughs should be. For some reason the filmmakers also felt a need to over-stuff it with plot, bringing in a murder conspiracy involving Harry's daughter's stepmother.

The problem is the plot isn't worth it, the film becomes 20 minutes longer than it needs to be because of it, and it still isn't funny.

Directors: Peter Farrelly, Bobby Farrelly

Running time: 109 mins

Kon-Tiki (15, 116 mins)

Directors: Joachim Rønning, Espen Sandberg

3 stars

Don't be put off by the fact that this well crafted Norwegian drama was up for best foreign film as far back as the 2012 Oscars - its years in the wilderness having more to do with the vagaries of distribution than a reflection on its quality.

Still, more might have been expected from the story of real life adventurer Thor Heyerdal, who in 1947 set out on an all or nothing trip to prove that Polynesia was settled from South America and not Asia.

Using only the sort of balsawood raft that would have been used 1500 years earlier, the trip starts gently enough as Heyerdal and his crew set out from Peru. Aside from some early trouble with navigation and finding the correct current, there's not a great deal of incident or peril, with a bit of a storm and a few sharks the worst that is thrown at them.

Nor is there much opportunity to get to know the personalities on the boat (there are six of them) beyond Heyerdal, but it's his ego that drives the trip and the film on. In the end it's a handsome adventure that offers a pleasant tour of the Pacific while being frustratingly light on adventure.

Directors: Joachim Rønning, Espen Sandberg

Running time: 116 mins