Parents who wish to shun the shouty, sparkly shows this Christmas, fearing perhaps that they are the theatrical equivalent of e-numbers, are heartily encouraged to consider Hampstead's nourishing fare.

Artistic director Anthony Clark, taking a break from new writing for grown-ups, has produced a fluid adaptation of Ian Whybrow's popular children's book and the result is two hours of gentle yet engaging storytelling. At the matinée I caught, my fellow audience members were quite the most enrapt youngsters I have encountered this December.

A simple but crucial problem is bothering Whybrow's Wolf family: Little Wolf is a hopeless goody four paws. Growling, stealing and all-round naughtiness are quite beyond him, so parents Grizzle and Gripper decide that a spell at Cunning College will be his only hope.

Uncle Bigbad is the principal and no one knows better than him the Nine Rules of Badness. One of the most obvious charms of this piece lies in its verbal inventiveness. Little Wolf is on continual lookout for "lipsmackerous" food such as mice pies; a bad day leaves him feeling "sad and down and dumpy".

Little is, parents will be pleased to learn, a literate sort of chap, as he writes a letter home each night recounting his journey through Frettnin Forest.

The five-strong cast, wearing wolfishly clever baseball caps with lupine faces on the visors, could perhaps make more of Liz Cooke's playground-like set, which is just crying out to be climbed over and slid down.

They certainly work hard, though, picking up instruments to join in with the two onstage musicians and singing heartily.

Grant Stimpson makes Uncle Bigbad a suitably bad-tempered creature, whereas Ilan Goodman's appealing Little manifests good-natured curiosity, as well as a surprisingly well developed moral compass. Pack the mice pies for a family outing.