The month was March, the year before Dr. Herman Tarnower was shot. The occasion was a trip -- with Jean Harris -- to the Caribbean. But when the two arrived at the doctor's Harrison, N.Y., estate, a terrifying surprise awaited Harris.

Her clothes, according to testimony from Tarnower's housekeeper, had been destroyed and left in her closet for her to find. And the person who had destroyed them, the housekeeper said, was Lynne Tryforos, her much younger rival.

"When Mrs. Harris returned from her trip she found some clothes that she used to keep in the downstairs closet next to the guest room ripped and slashed," said housekeeper Suzanne Van der Vreken under crossexamination by defense attorney Joel Aurnou as the Harris murder trial continued today. "She had several clothes -- I don't remember how many -- one had the sleeve ripped from the body of the dress; there was a slash in her evening dress, in all of her dresses, they were slashed and ripped. . . ."

"And neither you nor your husband, Mr. Van der Vreken, did anything like that?" asked Aurnou of the star prosecution witness.

"No," said Van der Vreken.

"There was another person you saw entering the house the Sunday before Mrs. Harris returned?" pursued Aurnou.

"Yes," said Van der Vreken.

"Did you tell the doctor the name of the person who was in the house?"

"Yes," said Van der Vreken, not volunteering an inch.

"Who was it?" asked Aurnou.

"Mrs. Tryforos," said Van der Vreken.

Former headmistress of the Madeira School in McLean, Va., Harris, 57, has been charged with second-degree murder in the shooting death of Tarnower, her lover of 14 years. The defense has maintained the shooting in March was a "tragic accident," a suicide attempt gone awry. The prosecution, noting that Tarnower had been dating Tryforos, a woman 20 years Harris' junior, has maintained that Harris shot Tarnower, 69, in a jealous rage. Prosecutors have also, chiefly through the testimony of Van der Vreken, presented Harris as a woman scorned, a woman who would place several calls to her lover as he spent a weekend with another woman. They have portrayed Harris, on the night of the shooting, as throwing her rival's possessions about his bedroom in a rage.

But today, in a courtroom drama that unfolded with the twists of good soap opera, another side of the story emerged. Under questioning from defense attorney Aurnou, Harris was revealed as a woman who played an important part in Tarnower's life in even the last years of the affair. She seemed to threaten and anger her rival perhaps as much as her rival angered her. Harris was, moreover, aware of Tryforos' anger, and concerned that she might attack again.

Under questioning from Aurnou, Van der Vreken, a woman with a markedly selective memory, admitted that she had kept some of Harris' clothing in her own closet after the original attack. There also seemed to be the suggestion, from Aurnou, that Tryforos may have made anonymous phone calls to the doctor at home.

"Incidentally, from '75 right up to March '80, did the doctor ever receive at his home anonymous phone calls?" Aurnou asked Van der Vreken after a line of questioning about when Tryforos and Van der Vreken first met.

There was an objection from the prosecution.

"Did you receive annoying phone calls?" said Aurnou.

There was another objection. An answer never came.

The testimony of the witness today was given particular credibility by her reference to her household record books, journals in which she noted who came to the doctor's home for dinner, who stayed overnight and when the doctor went away on trips.

Those accounts -- reportedly kept so that Van der Vreken never served guests the same meal twice, a dreadful gaffe in this part of the country -- caused a sensation in the local press. ("Maid kept love diary of swinging diet doc," trumpeted the New York Post, which has seized on this case with gusto.)

But the journals, which the housekeeper had balked at bringing to court, also gave a definitive picture of Tarnower's relationship with both Harris and Tryforos, a relationship -- or relationships -- best characterized as a romantic swinging door. Under questioning from Aurnou, Van der Vreken, admitted to the doctor would often return from a trip with one woman, dine the next night with another.

"Look at the early [in the record] October 1976. Does that refresh your memory about whether Dr. Tarnower took a trip to Europe at that time? To Warsaw, October 16th?" asked Aurnou.

"Yes," said a chilly Van der Vreken. "And who came home with Dr. Tarnower?" asked Aurnou.

"Mrs. Harris," said Van Der Vreken, in her heavy accent.

"And whom did Dr. Tarnower have dinner with the next night?" asked Aurnou.

"Sev-er-al people," said Van der Vreken, still the loyal and discreet servant.

"And was one of those se-ver-al people Mrs. Tryforos?" asked Aurnou, mimicking her accent.

"Yes," hissed Van der Vreken.

"And did she stay over?" asked Aurnou.

"Yes," said Van der Vreken.

The household journals were not, however, all-encompassing. Missing were the records from 1967 and part of 1980, a gap which, with Van der Vreken's well-known hostility to the defense, made for some cynical remarks in court.

"You looked everywhere?" asked the defense attorney, his voice mildly sardonic. "You searched high and low?"

"Yes," said Van der Vreken, unsmiling.

When she left the stand in the break that followed, Pearl Schwartz, sister of the late diet doctor, smiled broadly and, in front of the crowded courtroom, gave her a hearty pat on the back.