How a country newspaper won a Pulitzer; The Light on Synanon, by David Mitchell, Cathy Mitchell, and Richard Offshe. New York: Seaview Books. $11.95.

"The Light on Synanon" is the stuff that those wonderful old movies from the 1930s and '40s were made of. In this scenario, a struggling, ambitious young couple (played by Spencer Tracy and Katharine Hepburn) scrape together the down payment on a floundering country newspaper. Setting up both home and shop in the tiny, antiquated newsroom, they dedicate themselves to serving their small readership with thorough and insightful local news coverage. In due course they run up against a locally based corrupt corporaton, the heinous crimes of which go, unchecked by the town's intimidated law-enforcement officials.

Despite possible danger to themselves, the gutsy young publishers are relentless in exposing the corporation's dastardly deeds, which include kidnapping and child abuse. But progress is slow, and their marriage almost breaks up under the severe strains. At one point they even put the paper up for sale. The happy ending, however, is just around the corner, investigation and a Pulitzer Prize.

But the best aspect of the story is that it's not an old movie -- it's a modern real-life event. The young publishers are Dave and Cathy Mitchell who bought the Point Reyes Light in 1975, a weekly serving 3,000 or so readers on unchic coastal side of California's affluent Marin County. The corporation they helped expose is Synanon, a once highly regarde ddrug rehabilitation center that turned into a counterculture Mafia. As unsavory reports of kidnappings and brutal beatings reached the newspaper office, the Mitchells, together with Berkeley sociologist Richard Ofshe, began investigating.

Co-authored by the three-some but written from the point of view of Dave Mitchell, "The Light on Synanon" is an engrossing and suspenseful account of that investigation. It was, the authors reveal, a tedious and frustrating task that did not show tangible results until late in 1978, when the notorious rattlesnake attack on attorney Paul Morantz by Synaron officials forced the issue into national light.

Suddenly the months of seemingly fruitless work were taken seriously both on the home front and by the national press, which began streaming through the Mitchell's office. In April 1979, about a year and a half after the Light published the first Synanon story, the paper won the Pulitzer Prize for Meritorious Public Service. But far from marking the end of their investigation , the Mitchells have continued coverage of Synanon (currently fighting back on a number of civil lawsuits and criminal cases) to the present day.

"The Light of Synanon" should be required reading for anyone who thinks a small newspaper can only serve a small purpose or that all the important news is in Washington or abroad. By digging in their own backyard, the Mitchells set an example for the entire world.