Despite being a former child star - or perhaps because of it - Jodie Foster makes precious few films aimed at younger audiences. Her last was Anna and the King in 1999. Before that it was Candleshoe, over 30 years ago.

On this evidence, she should do more.

Her engagingly goofy performance as agoraphobic children’s author Alexandra Rover keeps this excitable but rather leaky South Sea frolic afloat.

Alexandra’s adventurous alter-ego is Alex Rover, the rugged explorer whose exploits delight young readers from her native San Francisco to… well, to the volcanic island paradise inhabited by wide-eyed pre-teen Nim (Breslin) and her widowed dad Jack (Butler).

After agreeing to leave Nim alone for a couple of days (“I’m not a little girl anymore!” she tantrums), Jack sets sail for specimens. But a storm leaves him stranded at sea.

Thanks to creative plotting involving mistaken identity by email (the movie gods move in mysterious ways), Alexandra fearfully begins an epic journey by land, air and sea to save #1 fan Nim.

Meanwhile, safe in the knowledge that Alex Rover is on the way, Nim conspires with her animal friends – a croaking lizard, a flatulent sealion and the pelican equivalent of Lassie - to scare away the obnoxious passengers and crew of an Aussie cruise ship who have descended on the island.

Believe it or not, it’s easier to follow than it sounds. But with Butler also playing the fictional Alex, frequently appearing to chivvy the real Alex along, it’s still unnecessarily convoluted.

After their assured debut Little Manhattan, it’s surprising that husband-and-wife directing team Flackett and Levin have such an uncertain grasp on Wendy Orr’s 2002 novel.

Enthusiastic scene-hopping isn’t enough to pull Nim’s Island from an undercurrent of storytelling iffiness.

Is it really okay to use animals as projectiles? What kind of single father leaves his only daughter alone in the wilderness? What brought about Alexandra’s psychological condition – she’s only had it for 16 weeks? And why is she only a neatness freak when it comes to her desk?

What does it matter? A well-placed heart and committed performances make this as appealing a portrait of mental instability and irresponsible parenting as you’re ever likely to see.

Elliott Noble