Part thriller, part social critique, writer-director James DeMonaco's $3 million entry The Purge last year grossed more than $89 million worldwide - a sure sign a sequel would follow.

Happily, unlike most horror sequels, The Purge: Anarchy, which opens Friday, isn't a cheap knock-off but an equally effective, deliciously disturbing movie. It's bound to delight genre fans (and dismay critics, who attacked the first as heavy-handed and sloppy).

The Purge: Anarchy further develops the series' conceit: America in the near future is a haven with virtually no unemployment, a low crime rate, and a thriving economy. The nation owes its transformation to the Purge. Once a year for 12 hours, Americans may commit any crime - murder is recommended - without prosecution.

This bacchanal of blood gives folks a chance to exorcise their rage and frustration. It also has a social effect: Since most victims are poor, sick, indigent, or undocumented, the Purge culls the population, saving the government untold dollars.

The Purge was a claustrophobic chamber piece about one family's attempts to keep murderous intruders out of their house.

Blessed with a larger (undisclosed) budget, The Purge: Anarchy is splashed across a much wider canvas. DeMonaco opens up the story with multiple locations, more characters, and an intricate, if sometimes puerile, plot.

Frank Grillo stars as a Man With No Name equipped with an armored muscle car and a huge gym bag full of guns 'n' ammo. He plans to use the Purge to avenge the death of his young son.

Straight out of a spaghetti western, Grillo's character is a man of few words whose stoic exterior masks an inner life rent by torment and tragedy. His mission is interrupted when he decides to help several people stranded on the street, including a spoiled yuppie couple (Zach Gilford and Kiele Sanchez) and a diner waitress (Carmen Ejogo) and her younger sister (Zoe Soul).

Impressive, blood-soaked set pieces follow as the group is attacked by legions of homicidal maniacs on their way across Los Angeles.

DeMonaco livens the proceedings by introducing a new type of Purge villain, the super-rich. Too civilized to hunt themselves, they send out mercenaries to round up victims and corral them in swanky killing clubs.

But the film enters Monty Python territory as it shows society's high and mighty in resplendent gowns and black tie bidding thousands of dollars for the right to finish off one poor sap or the other.

Things go from strange to silly with the entrance of a group of revolutionaries that wants to destroy the Purge.

However, if you accept its goofy premise, The Purge: Anarchy will give you a mighty fun time.

The Purge: Anarchy **1/2 (out of four stars)

Directed by James DeMonaco.

With Frank Grillo, Kiele Sanchez,

Zach Gilford, Carmen Ejogo, Zoe Soul.

Distributed by Universal Pictures.

Running time: 1 hour, 43 mins.

Parent's guide: R (adult subjects, profanity, strong bloody violence).

Playing at: area theaters.