Somewhere under the cloudy skies of China's Szechwan Province, Chang Hsi-ting and her husband, Liu Chieh-ting, two earnest Communist in their 40s, stand on a stage and watch an angry crowd drown the hopes of their lifetime in curses and catcalls.

This is the anniversary of the fall of China's infamous "Gang of Four," the quartet of powerful Peking and Shanghai politicians whose nighttime arrest a year ago last Thursday ended a decade-long effort to put Chairman Mao Tse-tung's most radical ideas into practice. The winners of last year's power struggle announced on Thursday in a joint editorial in China's three leading publications that they are still not satisfied that those ideas - no longer attributed to Mao - have been cleansed sufficiently from Chinese political life. A new campaign to "expose and criticize the Gang of Four," their followers and policies is under way, the editorial announced.

As a result, Chang and Liu, perhaps the most interesting of the gang's disciples, have been sent back to their native Szechwan on the direct orders of Chairman Hua Kuo-feng for a series of public "struggle" sessions. Provincial broadcasts reveal three such public trials have already been held to inflame popular outrage at the couple and powerful patrons like Mao's disgraced widow, Chiang Ching.

Szechwan, China's most populous province, has 80 million people, more than all but seven countries in the world. It is the place where local party leaders once imprisoned Chang and Liu and allegedly tortured their two smallest children, where the young couple subsequently rose to the pinnacle of power and where they fell again into disgrace in a frantic attempt to recoup their losses. Last year they earned their new role as real villains in a Chinese Communist version of a traveling morality play. Bloody Vendettas

CHANG AND LIU'S story, one of the most detailed and personal to come out of China in the last decade, tells something about the untold numbers of dissidents in China who no longer control the media that could tell their side of what has gone on in the last year. It reveals how deep are the emotions and how bitter the history that Hua and his colleagues must somehow erase if he is really to achieve his announced goal of "great order across the land."

Chang and Liu symbolize two decades of often bloody vendettas in Szechwan that, judging from recent official broadcasts, have not yet entirely ended. On one side are veteran party officials committed to proven methods of hierarchical management and steady economic growth. On the other side are thousands of workers, students and younger officials like Chang and Liu, fired by Mao's dream of creating a truly classless society through a permanent revolution, who feel they have been held back only by old men with old ideas.

This feud spilled so much blood in Szechwan in the late 1960s and more recently that the issues may not matter much now. The wronged just want to get even. And Hua's new post-Mao leadership in Peking seems to realize that the political pendulum could swing back against them if they do not completely wipe out the influence of the likes of Chang and Liu.

"The Gang of Four would not fall if we did not hit them, and, though have fallen, their poisonous influence will not vanish of itself if we do not criticize it," Thursday's editorial said. "Unless they are throughly criticized, the counter-revolutionary ideology and line of the gang might be rekindled from the embers when the time and conditions are suitable."

Chang and Liu have told most of their story when they were riding high. Other sources, such as Red Guard publications of the 1960s and official reports on Szechwan disturbances over the past year, corroborate much of their account. Like all good stories, this one has a villain - Li Ching-chuan, the former boss of Southwest China whom Chang and Liu kicked out of power in 1967, only to see him return to favor six years later and rise to an important position as troubleshooter for old cronles in Peking like Vice Premier Teng Hsiao-ping.

In the early 1960s, Chang and Liu served as Communist Party officials in the city of Ipin, 120 miles south of Szechwan's capital at Chengtu. Mao's plan for rapid economic development called the Great Leap Forward had just collapsed and the couple began to prosecute those officials under their jurisdiction who had shown less than wholehearted devotion to the controversial campaign.

However, in 1962, when a Peking leadership temporarily out of Mao's control officially scuttled the Great Leap, Li Ching-chuan, as leader of Szechwan, began to reinstate those officials in Ipin and elsewhere who shared his belief in the superiority of careful planning and technical expertise over political enthusiasm.

Chang and Liu vigorously objected to reversing verdicts on any of the erring officials, Li had both of them suspended from their posts. Undaunted, they sent a barrage of letters and telegrams to Peking, demanding a chance to expose Li's actions before central leaders. They got no response and began to accuse Li's friends in Peking, including Teng Hsiao-ping, of turning all their petitions back to Li. Li had enough.He called the couple to Chengtu on a ruse and had them thrown into a secret prison on the outskirts of town.

In a long description of their two-year imprisonment, Chang said Li and his aides tried everything to end her and her husband's determination to carry their case to Peking, which was their right under party rules. The couple lived in cramped separate quarters and were rarely allowed to see each other or their children.

"One evening," said Chang, "through my cell window I suddenly saw my two youngest children in the prison yard. One of them was 4, the other 5, I was anxious, and asked the block warden: 'How did the children get here?'

"He replied, "The upper level ordered it. You tell them to come into the cell.'

"I then brought them in. When the children saw me, they said nothing, not even crying out 'Mama!' I asked them, 'How did you get here? Who brought you here?'

"The children said nothing. I said, 'Do you recognize Mama? Why don't you speak?'

"The children started to cry, I said, 'What are you afraid of? . . . Don't be afraid, Mama is here.'

"The older child then burst into tears. I do not know how they tortured the children."

Chang said she and Liu were drugged and questioned harshly for extended periods, interpersed, in classic interrogation style, with periods of gentle persuasion to tell all and be released.

They would admit nothing, a stonewall tactic that may in part explain why they are today being made into such examples. They constantly wrote reports to Li complaining of their situation, certain in their belief that Li's secretaries, with typical Chinese devotion to bureaucratic detail, would carefully file each report in the provincial archives where they might eventually be unearthed to be used against Li. Escape to Peking

LI HAD BOTH Chang and Liu expelled from the party and transferred to a party hostel in Chengtu where they still could be carefully watched. But by 1966, Chang and Liu had become aware of the beginning of Mao's attack on the entrenched bureaucrats in the party - what would become known as the Cultural Revolution. One warm June night, Liu leaped over the hostell wall and, clutching a long expose of Li and his activities in Ipin, got on board a train bound for Peking. It was a daring act that would eventually lead to months of chaos in Szechwan.

Red Guards from at least 40 schools, some for Li and some against him, began to arrive in Chengtu. Chang, who eventually escaped herself, and Liu shuttled back and forth between Peking and Szechwan, organizing the anti-Li forces and supplying Chiang Ching and others with information.

Finally, on May 6, 1967, a fight between pro-Li workers and anti-Li Red Guards left 45 dead and 1,000 wounded.

"People were found everywhere lying in pools of blood," said a Red Guard, describing the aftermath of the incident at a Chengtu factory. "Half of the head of one Red Guard was blown away. The chest of one was pierced with a hole as big as a bowl."

Peking was forced to act. They removed Li from his posts and appointed a new ruling committee for Szechwan composed of Chang, Liu and two army generals brought in from outside the province. It was an impossible alliance. The solders wanted peace and order. Chang and Liu were committed to a permanent revolution where students and workers, led by people like themselves, would continually be criticizing and attacking old policies and old officials.

Gradually, both in Peking and throughout China's disturbed provinces, the soldiers got the upper hand. Chang and Liu dropped out of sight. An official broadcast last week revealed that on Christmas Day, 1969, "the party central committee issued a note on handling their problem. They were dismissed from all their posts inside and outside the party." However, "they constantly plotted a counterattack and a comeback."

Apparently still under the tacit protection of people like Chiang Ching, Chang and Liu characteristically never gave up. Last year "they impatiently jumped out, manipulated and directed their factional confederates, and caused an uproar in Szechwan and confusion in Chengtu with the result that those places knew not peace," one broadcast said.

Hua came to Chengtu in June of last year and "pointed out that the verdict on them could not be reversed," so they "launched a frenzied counterattack and pointed the spearhead of attack straight at Chairman Hua."

When Chiang Ching and company were arrested in October, Chang and Liu kept up the fight "with 10 times the frenzy and 100 times the hatred," said last week's official broadcast. "This really was reactionary to the limit!"

They were apparently arrested and brought to Peking. Then Hua decided to send them "back to Szechwan, screen them in isolation and put them to the struggle," a broadcast said.

Last month, Chang and Liu were brought up on a stage in Chengtu for their first public denunciation. "When it was announced that those two bourgeois careerists . . . were being brought to the dock, the comrades at the rally gave vent to their wrath and furiously shouted, 'Smash the bourgeois factional network!'," and official report said.

It was 10 years to the day after Li Ching-chuan had been forced to make his first appearance before a screaming mob at the direction of his two young tormentors. It is not likely that this was a coincidence, for Li, now 71, has a long memory.