PHOTO BY CARLOS RODRIGUEZ / LIONSGATE

On the one hand: This movie has a bad script, an unappealing lead performance and a distinct lack of motivation and stakes.

On the other: It has a very good dog.

“Arthur the King” adapts the true story of a mutt named Arthur, who linked up with an adventure racing team and followed them across the treacherous Ecuadorian jungle. The real Arthur, as depicted by his owner and biographer Mikael Lindnord, was a plucky survivor and inspired a foundation for the protection of stray dogs.

The fictional version, moved to the Dominican Republic for unclear reasons, has a bit of a life-on-the-street backstory before running into Mark Wahlberg and crew (Ali Suliman, Nathalie Emmanuel and Simu Liu) in the middle of the adventure racing world championships. That sport, which I became aware of entirely due to this movie, tasks hardy teams of fit survivalists with trekking across untamed terrain for days at a time; unfortunately, this makes “Arthur the King” spend ample time explaining to the audience what its characters are doing and why.

That’s one of several weaknesses to the film, most of which are structural; while the dog is clearly the star, we spend more time with the racers as they squabble and overcome setbacks. While Emmanuel and Liu do their best to elevate the travails of what is essentially a hobbyist competition to the level of high drama, their lead doesn’t help; Wahlberg just isn’t trying very hard.

Fortunately, the back half is much more focused on canine matters. Arthur, played by an expressive pup named Ukai, carries the film throughout its third act; by the time we get to its dramatic post-race developments, even cat people will likely be weeping.

Does that add up to a good movie, or just a good dog? It’s hard to say. But I think the film’s ambitions were humble: we were to leave very impressed at the bravery of both a real-life pooch and its on-screen counterpart. In those respects, it was a success.

Because it’s a very good dog.

My Rating: 6/10

“Arthur the King” is now playing in theaters.