When the two got to Carl Schurz Park around 4 P.M. that Thursday, May 22, they saw a familiar tableau of serenity and release: the sparkling East River, dogs cavorting, children scaling monkey bars and, of course, their teen-age friends, gathered along the chess tables and benches by the basketball courts, in the cool shadows of the trees.

Daphne Abdela was swinging a six-pack of Coors. Christopher Vasquez was staring blankly. She was a regular, but had not been around for two weeks, and the other teen-agers didn't remember her ever bringing him along. She had short brown hair and concealed her pudginess beneath her baggy grunge clothes. He had rimless glasses and a fade haircut. She had already started drinking, her friends recall. Before the night was over, he would be seen drinking, too.

She was a familiar presence to evening congregants of both Carl Schurz, the park surrounding Gracie Mansion, and Central Park. A brash young woman with rich parents, she found comfort crossing the borders of class to consort with teen-agers who knew little of the privileges of wealth. He was newer to this scene, a haunted young man from a working-class family.

In the last week, of course, the two 15-year-olds have become notorious as suspects in the vicious killing of a 44-year-old real estate broker in Central Park. The victim, Michael McMorrow, was stabbed dozens of times and disemboweled before being heaved into the Lake. More than a week after the murder, the police say they still don't know why it happened. They don't know what, if anything, the victim may have wanted of the teen-agers, or what, if anything, the teen-agers may have wanted of him. Their lawyers say they are innocent. Mr. Vasquez's lawyer will not comment on the case, though Benjamin Brafman, Miss Abdela's lawyer, said that only Mr. Vasquez was responsible for the murder.