When Calvin Levels was preparing to play Wayne Williams in "The Atlanta Child Murders," he went to Atlanta in to talk to the man he was to portray. The interview fell through, but while he was in town, he stopped at a rally organized by mothers of some of the victims. Afterward, Levels recalled, he talked with nine or 10 of the women.

"We didn't get up from the table until 2:30 a.m.," he said. "Every mother told me her story. And cried. There are still 27 unsolved kids' murders. The mothers wanted the case solved. They wanted to know who killed their children."

That urge to know more about the case might be contagious and could be caught by viewers who tune in this week to "The Atlanta Child Murders," a two-night, five-hour CBS miniseries beginning tonight at 8 ad concluding at 8 on Tuesday.

"My feelings propelled me to give 100 percent of what I had to give as an actor," said Levels. "From what I found out in Atlanta, by the time I started playing the part I was so enraged that the information I'd found had not been brought out in the open . . . I think it helped my performance. I wanted to have this information out in the open . . . If the performances are solid, many people will be moved to do something about it . . . I channeled all the anger and hurt into my performance."

The crosscurrents of emotion generated by the original case and this recreation run strong and deep. In July 1979 the bodies of two black youths were found near each other in southeast Atlanta. In November there was another, and still more followed. As the body count mounted -- consisting mostly of poor black males between 9 and 16 -- national attention turned to Atlanta, with the series of killings perceived as related. In July 1980 a police task force was formed. In June of 1981 Wayne Williams, an erstwhile music promoter in his mid- 20s, was arrested and charged with killing two adults on the 29-name list of victims. When he was convicted in February 1982, the task force was disbanded, the case officially closed. Left open in some minds, though, were many questions: Who was responsible for the other 27 victims? And was Williams really guilty?

"At first I wasn't sure," said Levels. "I thought they simply needed someone (to arrest and convict) to quiet the unrest in Atlanta . . . Then I started my research."

Williams, he found, was a fellow with a less than endearing personality, whose arrogance was thought to have hurt him during his trial. "He could very well be the guy who did it," said Levels. "I couldn't decide. My final decision was that he did not kill anyone. But he could have been involved."

The miniseries was directed by John Erman, who gave "A Streetcar Named Desire" its distinctive look for television and whose credits also include "Roots." The teleplay was written by Abby Mann, who shares billing as executive producer with Gerald M. Rafshoon. Mann also wrote "Judgment at Nuremberg" (for the TV and movie productions, winning an Oscar in 1962) and "The Marcus- Nelson Murders," the highly respected pilot to the "Kojak" series. He put the slant of the show in sharp focus, calling the Atlanta case "a national tragedy" and expressing "grave doubt" about Williams' guilt.

Mann's feelings are also shared by one of his central players. Levels said he believes children are still being done away with in Atlanta. "The press is not reporting it, TV is not reporting it," he said. " . . . Nobody wants to hear about it, nobody wants to talk about it."

"Atlanta" may be the vehicle that has people wanting to talk more about Levels. Born in Cleveland 30 years ago, Levels' previous TV outings include two 1981 movies, "Side Show" and "Crisis at Central High," in which he played the student who integrated the school in Little Rock. Sharp-eyed movie-goers might recall him as Coalhouse Walker's right-hand man in "Ragtime." Beyond that, his exposure has been generally limited to the New York stage, where he won the Theater World Award for his performance in "Open Admissions."

When Levels went to read for the part of Williams, Mann at first thought him too handsome for the part. "I replied that it was being able to recreate the emotional side of the character that was important, to build an illusion that will stay with an audience," Levels recalled. "They wanted me to be more arrogant, to have a superior attitude. I thought about my acting. I'm very confident of my talent. I did an improvisation for him. I said, 'Just a minute. Here I am the greatest actor in America and you guys are toying with the idea of hiring me?' "

Contract in hand, Levels -- who normally runs four days and pumps iron the rest of the week -- shut down his exercise program and ate everything in sight. Ice cream for breakfast became a favorite. With the addition of 30 pounds and an Afro wig, his transformation was complete. Now, "Atlanta" behind him, Levels is back on the track and in the weight room and is studying the production end of show business. But the experience of doing the child- murder story lingers.

"I'm not sure myself what I can do . . . " he said. "Outside of my art form, I'm not sure what I can do. I do know I plan to get involved with UNICEF and work against kids' starvation."