In the afternoon in the small church of Ciudad Barrios in northern San Miguel Province, the two U.S. priests had celebrated a solemn mass for the soul of their fellow Maryknoll priest, Roy Bourgeois, who had been missing in El Salvador for 12 days and was presumed to be dead.

It had been a sad occasion, recalled the Rev. John Spain, and that night he waited for the end of a Celtics basketball game broadcast on the U.S. Armed Force radio network so that he could catch the latest news bulletin before retiring for the night.

The announcer said that Bourgeois, a 38-year-old activist priest from Chicago, was alive and at the U.S. Embassy here.

As Spain later explained it, he ran upstairs to where his fellow Maryknoller, the Rev. Ron Michaels, was preparing to go to bed and shouted: "Ron, he is alive, he is alive."

"That was the good news," Spain said the other day. "Then we heard the rest -- that instead of having been kidnapped a we had all suspected, Roy had disappeared on his own accord to go visit with the rebels."

That news sent waves of apprehension through the tiny Maryknoll community here. None of the four U.S. priests and two nuns scattered over the countryside needed to be told what Bourgeois' strange personal odyssey to commune with the guerrillas in the hills meant. He could single-handedly have jeopardized the work of the Maryknoll order in El Salvador and possibly in the rest of Central America as well.

The El Salvador government, smarting from the embarassment of the still untried murders in December of three American nuns and a lay worker here -- two of them Maryknollers -- took the opportunity to portray the incident in a larger context. The armed forces, which have been implicated in the missionaries' slayings, immediately issued a statement saying that Bourgeois' actions "had destroyed his moral authority and put in doubt the honor and serenity of the order to which he belonged."

The Maryknollers, accustomed to the veiled threats of authorities who accuse them of practicing a sort of Christian Marxism because of their insistence on identifying with the poor and the oppressed, wasted little time in leaving their parishes in the countryside to gather quietly in San Salvador. There they decided, after much anguished soul-searching, to leave for their order's regional headquarters in Guatemala City until the latest round of criticism by El Salvador's military leaders subsides.

The incident served to underscore once again the virulent suspicion with which this small, dedicated U.S. missionary order of priests and nuns is viewed among the traditional landowning and military ruling classes of Central America. It is a suspicion that far overshadows their small numbers -- only six in El Salvador, 35 in neighboring Guatemala, and a smattering elsewhere throughout Central American.

The hostility stems from the mission of the order, founding in Ossining, N.Y. in 1912, to serve the poor, the exploited, and the powerless. In an area where neofeudalism is still the dominant form of power, such a stand is viewed by conservatives, especially in El Salvador and neighboring Guatemala, as nothing short of sedition -- a dangerous destabilization of the traditional social orders that the landed and military oligarchs have always controlled.

The Maryknollers' reputation has been further tarnished by the activism of a handful of their more celebrated colleagues. In 1967 four Maryknollers in Guatemala were ordered by their superiors to leave the country because of their open support for a since-suppressed guerrilla movement. Although the order expelled them when they refused, the image of the guerrilla priest has stuck much to the chagrin of the order.

It is an image that was reinforced in 1979 in Nicaragua when the dictatorship of Anastasio Somoza was overthrown and a Maryknoll priest, the Rev. Miguel d'Escoto, for 10 years the head of the order's publishing house, was named as foreign minister of the new revoluntionary government.

Their close integration into the rural villages and urban slums of Central America, where the seeds of dissent often grow into revolution, has sometimes brought Maryknollers, and members of other orders as well as the local clergy, into direct contact with guerrilla organizers and militants. As local governments well know, little goes on in such small communities of which church representatives, usually the only other authority figures besides those of the government, are not at least peripherally aware.

Maryknollers working in Nicaragua during that country's 1979 revolution later told of a secret nighttime village meetings where peasants prepared for revolution, and of heated battles during which guerrilla fighters appeared at their doors asking for aid and asylum, which usually was given.

But the priests and nuns, although imbued with the overwhelming antigovernment sentiment among the people with whom they worked, and intimately aware of abusive government activities, largely tried to stay out of direct association with the discussion and planning of revolution.

In El Salvador, popular sentiment is largely against the government but there is much less evidence than during Nicaragua's revolution of extensive support for the guerrillas. Although it is easier to work among the poorer sectors here without risking involvement in revolutionary activities, it is more difficult to convince the military that such involvement does not exist.

Salvadoran government troops often are indiscriminate in their labeling of peasants as guerrilla activists or supporters, and their suspicion of possible subversion is magnified in the case of the priests and nuns who travel among, and influence, the poor.

The activities of Father Bourgeois, who came to El Salvador ostensibly as an interpreter for a Chicago television station, have served largely to feed the suspicions of military conservatives here that the church in general, and Maryknollers specifically, are promoting and perhaps even organizing revolution.

But visits to Maryknoll missions in Central America revealed activity no more revolutionary than siding with the poor in their social and economic struggles and trying to help them learn how to help themselves.

"We are not even here specifically as Maryknolls, but as priests," Michaels said shortly before flying to Guatemala. "We work in a parish that encompasses 80,000 to 100,000 people and we are there because the present archbishop of El Salvador asked us to go there and minister to the region where there are not other priests."

Because suspicion and fear run so high against the church in this violence-torn land, the U.S. priests find that their work is tightly proscribed. "What we do here is pastoral work, that is about all we can do in this situation," Father Michaels said. "You know, baptisms, communions, marriages -- and a lot of burials."

The two priests, like another in the guerrilla-besieged province of Chaletenango, are basically itinerant priests in areas where the church has long been absent.

Sister Madeleine Dorsey, a blue-eyed and greying-haired nun, who for the past five years has worked among the poor in the Lamatepec district of Santa Ana, does the same, as does her cohort Sister Teresa Alexander. The district, which encompasses some 8,000 people, 85 percent of which are unemployed, has been an area of great activity by the rightist squads that throughout the country operate in the night against suspected leftists, or anyone who might even be considered a potential leftist, such as students and young professionals.

Sister Dorsey says that she sees her role as "accompanying the people, being available to them, trying to respond to their needs," the 62 year old nun said. "Right now all we can do is to be with these people, to share with them, because they are hurting very badly."

Not wanting to comment on the actions of Father Bourgeois, who came in from the outside and does not have to continue to live in El Salvador and work, Sister Dorsey declined to judge his actions. She said she had enough problems as it was.

"Just to take a strong stand for the poor," she said, "you kind of get yourself in trouble."

All six of El Salvador's Maryknolls said before their departure that they were only going out for a conference and that they hoped to return to the people they serve in a matter of days.