Australian writer-director P.J. Hogan had a mid-1990s international hit with “Muriel’s Wedding,” introducing much of the world to actress Toni Collette as a marriage-obsessed dreamer.

The two pair up once more in “Mental,” in which Collette again plays a woman bending reality to her whims. But this time she’s a wild-eyed, avenging angel: think of her as a female McMurphy from “One Flew Over the Cuckoo’s Nest,” but returned to the street and plenty angry.

Hogan creates an outré, hyperreal satire around Collette’s heroine, Shaz, as she moves in on a clueless family and takes over. Barry (Anthony LaPaglia), the patriarch, is an absent dad and philandering mayor of a coastal town. His desperate wife, Shirley (Rebecca Gibney), is in a mental hospital after recent manic episodes, including one in which she enacted her “Sound of Music” fantasies on a suburban street.

That leaves the broken couple’s five young daughters unattended, which Barry fixes by turning a knife-wielding stranger — Shaz — into a live-in nanny.

In short order, the charismatic, impulsive Shaz has the girls convinced the reason they feel ugly, crazy and unwanted is because they are highly evolved and everyone else is nuts.

Certainly there is ample evidence Shaz is right. Kerry Fox is fun as a neat-freak neighbor scrubbing her driveway with a toothbrush, and Caroline Goodall is a sight as Shirley’s sister, fixated on dolls.

The heart of Hogan’s film is in the right place, and Collette is masterful as an agent of anarchy. Among the young actresses playing sisters, Lily Sullivan is terrific as a teenager rebounding from self-loathing. There’s also unexpected pleasure in Liev Schreiber’s colorful turn as a grizzled hunter of sharks.

But Hogan doesn’t know when to quit. “Mental” feels like it has several endings, each more distorted and uncontrolled than the last.

That mars but hardly destroys the movie, which largely feels like an amped-up urban legend.

Tom Keogh: tomwkeogh@yahoo.com