Cheryle L. Wallis, the victim of a February knife attack in Arlington, described in court yesterday the khaki parka, blue jeans, green-knit cap and black hair of her assailant. She also said she had seen those clothes before -- on a person who lingered across the street after a fire last December in the house where she lived.

Mary F. Prevost, 24, of 2001 N. Adams St., Arlington, is charged with attempted murder in connection with the wounding of Wallis, who lived with Prevost's former boyfriend. She also is charged with arson in connection with a fire Dec. 17 at the South Arlington house her former boyfriend, Robert Hogue, 26, and Wallis shared.

After a three-hour preliminary hearing yesterday in Arlington General District Court, Judge Joseph Gwaltney ruled there was enough evidence to constitute probable cause and ordered the case to be heard by a grand jury April 21.

In her testimony, Wallis described opening the door last Feb. 26 to a messenger who carried a bouquet of roses and announced: "Flower delivery."

When Wallis asked, "For whom?" the messenger dropped the flowers and began slashing at Wallis with a kitchen knife, she testified.

Hogue said he had just stepped out of the shower that evening when he heard a commotion downstairs. "I threw [the bathroom] door open and went out to the top of the stairs," he said. "I saw a man with a moustache, a green hat, a parka and a hood force Cheryle into the house; he appeared to be punching her."

Hogue testified he chased the messenger into the snow, and caught and wrestled the attacker to the sidewalk. In the struggle, "the person's hat came off and with the hat, the person's hair came off," he said.

"Did you recognize the person?" asked Assistant Commonwealth's Attorney Arthur Karp.

"Yes," Hogue said.

"Who was it?"

"Mary Prevost."

Wallis, 28, testified seeing "someone unusual directly across the street" after the early-morning blaze in December.

Prevost, who has been held in a secure ward at the Psychiatric Institute of Washington, attended the hearing but did not testify.