The padlock on Reinaldo Arenas Fuentes' front door had suddenly changed. The rusty old lock, which residents of the apartment building had seen for years, was replaced one morning last week with a new, shiny and differently shaped lock.

The small telltale sign had to be an important augur.

Arenas was well-liked and even privately admired among the official pundits of culture. But he also faced problems since he was a dissident, a writer and served a jail term for a homosexual offense.

His novel "Celestino Before Dawn" was published by the government, yet a second. "The Skunks," had been smuggled out of the country and published.

Arenas lived in the moldy 19th century apartment building for many years and his neighbors knew him as a "quiet" boy."

One of the men on his floor offered a whispered explantion for the presence of the new lock.

"Reinaldo has been taken away," he said, grabbing his left wrist to imitate the act of detention. "Police came at 4:30 this morning, they had a clipboard with names, and they shouted his name from the street."

Later that day, the alarm was sounded at the Ministry of Culture, which got in touch with security officials at the Ministry of Interior. They wanted to know what happened to Aenas and, if he had been arrested, why.

Later Interior officials explained that police looking for people with police records to send to the United States picked up Arenas and told him he could leave by boat.

The news cause great consternation among the cultural officials.

"How terrible, we did not want Renaldo to leave this way. We wanted him to have an ordinary passport and fly to Panama or Costa Rica, so he could come back to Cuban whenever he wanted to," one high official said, groaning.

Another alarm went out to security to find Arenas, stop him, bring him back. For several hours a frantic search was mounted at the docks in Mariel, among the buses full of refugees and on Miami-bound boats.

No trace of Arenas was found and it is believed he was one of nearly 4,000 people who left that day.

Later one of Arenas' friends uncovered the mystery of the shiny new lock on the apartment door. After police took Arenas, loud noises were heard in the apartment and a frightened woman called for police. Inside they found Arenas' neighbor with an ax. He had chopped a large hole in the connecting wall and extended his one-room apartment.

To assert his proprietary rights, he put the new padlock on the door.

THERE IS currently a level of political fervor on Havan's streets that old-timers say they have not seen since the early days of the revolution -- not since the U.S. invasion of the Bay of Pigs.

Foreign press reports tend to describe it as mob violence, condoned and often instigated officially.

Yet on numerous occasions in the past week, police clearly had trouble controlling and toning down the taunting crowds that gather constantly in front of homes of people waiting to leave of the United States.

Given the pitch of the fury, it is perhaps surprising that so few people have been seriously hurt. Invariably the crowds fling stones, although not against windows, followed by a barrage of tomatoes and eggs.

They hang insulting placards on houses and heckle "traitors," but the excitement and resentment seems to go beyond mere Marxist ideology.

For two decades, Cubans have been obliged to make a Herculean effort for the big leap into communism and development. The new system imposed rigorous austerity and ideological piety on a people by who nature are gay, chaotic and undisciplined.

Many Cubans have thought the sacrifices worth the efforts, others doubt it, and many despair and want to flee.

Much of the anger, Cubans and foreigners alike agree, finds it roots in the return of about 100,000 relatives from the United States. For many years, these new tourists had been called "traitors." "gusano," the Spanish for "worms."

Yet in the past year they are seen around Havana as the privileged people who bring back presents, stay in expensive hotels, use taxis and eat expensive meals, which most people here can never afford.

A young woman who works as a government secretary watched one of the demonstrations against people wanting to flee a few days ago.

"I guess this riffraff will come back in a few years behaving as the chosen people also," the woman said. "The whole thing stinks; I just don't understand."

A NUMBER OF CASTRO supporters explained their resentment in terms of protest against "the opportunists" who posed as revolutionaries, got an expensive education and then opted out.

This explains perhaps why the most bitter attacks have been directed against departing government and union officials who have enjoyed the privileges of their rank and used their power to control those below.

Joel Arevalo, for example, was the secretary of the Union of Airport Workers. When he walked to a refugee plane bound for Costa Rica last month, only police protection prevented him from being lynched by the same airport workers he controlled for so long.

The home of Manuel Arrojo, secretary of the Union of the Armed Forces Civilian Workers, had his house painted and stoned. Many of the participants reportedly were members of his own union.