FIVE YEARS AGO a group of U.S. Senate telephone operators, realizing that leaves were being distributed with something less than fine impartiality, banded together and asked the sergeant-at-arms to write down the policies governing sick leave, annual leave and maternity leave. Candace Hanson of Upper Marlboro was one of those upstart telephone operators and less than a year later she found herself spending most of her time in Upper Marlboro.

The firing of Candace Hanson sounds at first like something out of the 18th or 19th century and when she tells it your first inclination is to think there's something more to it. It doesn't make sense. But Hanson, a $10,500-a-year telephone operator, took on the U.S. Senate back in the days when Congress was merrily exempting itself from civil rights acts it was passing and when women and blacks around town called the Hill the Last Plantation. If you keep that in mind, it's a little easier to believe what happened to Hanson.

There are, of course, two versions to what happened to Candy Hanson. Hers, which she has detailed in court papers and interviews, and the Senate sergeant-at-arms' version, which no one wants to talk about now. For a while they didn't have to. For a while a lower court agreed with the sergeant-at-arms that Hanson didn't have a case. But this month she won a major victory in her four-year fight when a higher court ruled that Hanson might have a case and ordered that she should get her day in court.

Hanson and her lawyer, Linda Berg, say that, first off, the sergeant-at-arms, F. Nordy Hoffman, and his administrative assistant, Ron Martinson, published the written leave policies reluctantly. Hanson says junior phone operators even lost leave time when the written policies were promulgated.

Then, she became pregnant, the first operator to do so under the new policy. She read the rules and realized that there was a discrepancy between the maximum amount of time (eight weeks) an employe could take, and the maximum amount of sick and annual leave a person could accumulate (six weeks). What, she began asking, happened during the other two weeks? Should she go on leave without pay? Would she lose seniority? Would she lose her health insurance coverage?

Hanson asked questions, got confusing answers, and decided to write a letter asking that the leave policy be clarified. "Her response," says Berg, was a very nasty letter from the sergeant-at-arms that the policy was clear and there was no way he could make it more clear and he fired her."

"On May 21," says Hanson, who was then six months pregnant, "the chief operator came down and said you have an appointment over at the Capitol. So we left. They never told me what I was going over for. I thought it was to answer my letter. I went over there, they took me into Mr. Martinson's office and they told me to sit down at this round table. He handed me this letter and told me to read it. I read it and what it boiled down to is they were terminating me. . . .

"Rather than clarification of the policy, they're saying I wanted modification of the policy, and you know something? You can't modify something you can't understand. I told Mr. Martinson I would turn this over to an attorney and he said, 'We are exempt.' That was his phrase. I couldn't believe anyone would just sit there and say 'We are exempt.'"

At the time, though, they were. That was before the famous case in which the Supreme Court finally ruled in 1979 that Congress was not above the law and that it was not immune from claims that it violated the constitutional rights of its employes. One upshot of the case was that it cleared the way for Candy Hanson to sue the sergeant-at-arms over the way she was treated.

The sergeant-at-arms case against Hanson is not altogether clear. Martinson declined to discuss it because it's still in the courts. The Justice Department lawyer who has been handling it declined to comment on it for the record. But according to one brief he filed, the sergeant-at-arms fired Hanson, not for asking for a clarification, but for "repeatedly" expressing her dissatisfaction with the policy.

Berg says that after Hanson was fired she had to fight to get her umemployment compensation. Her employers showed up at a hearing and tried to portray her as a "nervous and excitable employe who didn't get along with the other girls in the office," says Berg, "and that the maternity policy issue was "the final straw." Berg says she countered that by producing baby shower cards from Hanson's telephone operator colleagues and that Hanson finally won unemployment compensation.

Hanson's original case was thrown out by a lower court, which decided she had not established sex discrimination or that she had been injured. But this month the U.S. Court of Appeals, in a decision written by Judge Patricia Wald, ruled the lower court erred. Wald wrote that the sergeant-at-arms' maternity leave plan may, indeed, discriminate against women because it is unclear, and women "may have to struggle with the plan's ambiguity, risking discharge for seeking clarification, when men would not be subjected to this difficulty."

Then Wald took the situation a step further and suggested that Hanson's rights as a public employe to question and criticize her employer might well have been violated when she was fired. Wald strongly suggests that when Berg goes back to court she ought to see if the Last Plantation is covered by the First Amendment.

"It's really an outrageous case," says Berg. "It's the kind of thing that when you hear of it you can't believe someone was fired for this sort of thing."

No, you can't. Hanson, the wife of a policeman and now the mother of two, hasn't worked much outside the home since she was fired. No one wanted to hire her when she was six months pregnant and after that she couldn't find work that paid close to her $10,500 phone operator's salary.

Almost four years of litigation have passed, and all that she and Berg have won so far is the right to try their case in court. "I just really believe very strongly in what she is doing and I think a terrible thing happened to her," says Berg. Now they will go back to court and ask for Hanson's job back, for back pay and for money to compensate for damages.

I hope they win.