Last Thursday, the day after the body of a street vendor who had been shot was found on a bicycle path in Far Southeast, homicide detective Thomas Arnold was reminded he had only one day to close the case before his brief vacation was to begin.

After starting with almost no clues, Arnold began to develop some leads on Thursday. The next day, instead of leaving on a trip as planned, Arnold went back to work.

"Did you ever read a book and like it so much you don't want to put it down?" he asked. "That's the way I felt about this case."

On Saturday, D.C. police said, Arnold's persistence paid off. A 16-year-old youth who had escaped from a city juvenile detention facility was arrested and charged with felony murder in the death of the vendor, James T. Rose, 22, of 5300 James Pl. NE.

Rose's body was found by a bicyclist about 1 a.m. last Wednesday on a bicycle path along a wooded stretch in the 400 block of 56th Street SE.

Rose had been shot once in the chest with a small caliber handgun.Police said that Rose, who sold clothes and trinkets from a stand at various downtown locations, also was robbed of a considerable sum.

Arnold, along with 6th District detective Earl Bryant, began questioning dozens of area residents and persons who used the path.

Late Thursday, they got the piece of information that led to the arrest: Someone told them a youth who had a cousin who had committeed a robbery near the path. The detectives were given only a nickname for the youth and had no name for the cousin.

But through further questioning, the police found the youth and learned the name of the cousin. Police files listed the cousin as having fled from the Cedar Knoll juvenile detention center, where he was awaiting trial on charges of robbery and carrying a dangerous weapon.

Circulating the youth's picture in the area of the shooting, police continued their investigation.At 3 a.m. Saturday 6th District officers picked up a youth on the street.

He was charged as an adult with felony murder in the death of the vendor and ordered held under $15,000 bond at Oak Hill, a juvenile facility with greater security.

Arnold, 33, a member of the homicide unit for about 1 1/2 years, expects to take his vacation some other time.