The messenger had a slight build, a thin moustache and a green knit hat, and was carrying a bouquet of flowers in wrapping paper.

"Flower delivery," the messenger announced when Cheryle Lee Wallis answered the front door of her South Arlington house Wednesday evening.

When Wallis asked, "For whom?" the messenger dropped the red roses and slashed at Wallis with a seven-inch kitchen knife, forcing her into the house and onto the stairs, police said.

Upstairs, Wallis' boyfriend, Robert Hogue, had just stepped out of the shower when he heard screams.

"I cracked open the bathroom door, looked down the steps and there was someone stabbing my fiance," he said in an interview yesterday.

"I ran down the stairs; he saw me and ran."

Police confirmed Hogue's account of what happened next: While Wallis called the police, Hogue dashed naked into the snow, clutching a white bath towel in one hand, and chased the messenger. A few blocks from the house, Hogue said, he caught up, wrestled the messenger to the ground, and pinned one elbow behind the person's back.

In the struggle, the messenger's knit hat had come off. So had his black hair and his moustache. A voice said, " 'It's me,' " Hogue recalled.

He saw a few wisps of blond hair, rolled the messenger over and stared into a familiar female face -- the girlfriend he broke up with nearly three years ago.

"I was shocked. First it was shock; then it just stopped me," Hogue said.

Police arrested Mary F. Prevost, 24, of 2001 N. Adams St., Arlington, and charged her with one count of attempted murder. In a brief hearing yesterday in General District Court, Judge Francis E. Thomas raised Prevost's bond from $10,000 to $100,000 and ordered a psychiatric evaluation. Prevost is being held in Arlington County Jail.

Defense attorney Carl Womack, appointed to represent Prevost during yesterday's proceedings, said he could not comment on the case.

Wallis was treated at National Hospital for Orthopaedics and Rehabilitation for cuts on both hands, several scratches and one puncture wound. Police spokesman Tom Bell said detectives recovered a seven-inch kitchen knife outside the house, a bouquet of flowers on the porch and a black wig and moustache several blocks away.

Prevost is registered as a graduate student at George Washington University's School of Public and International Affairs. She was born in Montclair, N.J., and has no family in this area.

Hogue, 26, said he and Prevost dated when they were both undergraduates at George Washington University, but that they broke up during his second year at George Mason University Law School. He said she had never visited him or Wallis in the house.

Hogue, now a lawyer with the federal Office of Personnel Management, and Wallis, 28, manager of a dental office in Northern Virginia, plan to be married this summer. Yesterday, Hogue said, the two were concentrating on trying to recover from the shock of Wednesday's incident. "It just makes your blood run cold," he said.