The AMC (search) movie-theater chain is trying to stop the bleeding in its business plan — by offering a money-back guarantee.

In a marketing ploy the company hasn't trotted out since 1988's "Mystic Pizza," AMC took out newspaper ads saying it would refund moviegoers' money if they are unhappy with one of its features, "Cinderella Man." (search)

The gimmick is seen as a desperate move to resuscitate the $88 million Ron Howard-directed boxing flick which, as of Tuesday, had grossed a paltry $50.6 million after 26 days in release.

But it comes against a backdrop of one of the worst box-office slumps in Hollywood history, with 18 straight weekends reporting lower ticket sales than during the same period last year.

The promotional campaign came days after AMC, in an effort to achieve some economies of scale in a brutally small-profit-margin business, announced plans to buy its next-largest rival, Loews (search).

The acquisition would give AMC 5,900 screens in 450 venues across the country — and make it the country's second-largest theater chain.

The rebate ads appeared in markets coast to coast yesterday, touting Russell Crowe's tweeds-and-tears redemption tale as "one of the finest motion pictures of the year" — and offering "on the spot" refunds to anyone who disagrees.

Looking to put the offer to the test, a Post reporter went to a matinee show Wednesday on 42nd Street and sat through about 20 minutes of the flick — then walked out and asked a box-office attendant for his refund, explaining, "I just didn't like it."

There was some initial confusion — one employee said it is "against our policy to give money back for not liking a movie," and the cashier at first told our man that "If you don't have the ad, you can't get your money back."

But after a reporter demanded to speak with the manager, the cashier made a quick call upstairs — and the $10.50 was returned.

An AMC spokeswoman said only 50 people had asked for their money back Wednesday in the 150 theaters across the United States where "Cinderella Man" is playing, adding, "We don't expect it to get much higher than that."

The money-back deal is valid for as long as "Cinderella Man" continues its run, an AMC exec said. But act fast — she didn't know how long it would be before the company punched out Russell's lights for good.