On her doorstep in Columbia Heights yesterday afternoon, a letter from home awaited Kim Slaybaugh. Twelve hours earlier, the 24-year-old waitress at the American Cafe on upper Wisconsin Avenue NW had fallen 20 feet and died as she changed into street clothes after work.

Moments after midnight Thursday, Slaybaugh, a waitress since May at the restaurant just south of Mazza Gallerie, was in the employe locker room behind the second-floor restaurant, police and coworkers said. She had just completed her shift and was changing from her uniform. One other worker was also in the locker room.

"Off the locker room is a door that enters onto a catwalk where the air-conditioning equipment is for all the restaurants in the building," said Greg Carey, president of American Cafe restaurants. "Apparently she went in there for more privacy while she changed."

The catwalk, a narrow metal grating with two rows of railing on either side, is two feet above the drop ceiling of the Jenifer Cinema, which is on the first floor of the building.

Slaybaugh's wallet fell onto the acoustical tiling of the drop ceiling. She apparently tried to retrieve the wallet by climbing down onto the ceiling, Carey and police said. She fell through the tiles, which are not meant to support any substantial weight, according to Ken Reed, vice president of CSM Management, the building's property manager.

Slaybaugh fell about 20 feet into the stairwell of the movie theater and landed on her head, police said. The other employe in the dressing room heard a crashing noise, and called police and a rescue team, but it was too late. Slaybaugh died instantly, police said.

Carey said it was unusual for any employe to use the catwalk as a changing area. Workers generally use either the locker room or the adjacent restrooms, he said.

The door between the locker room and the catwalk is not locked, Carey said. It is the only access to the catwalk, Reed said.

"It's just a tragic accident for which there's no good explanation," Carey said. Yesterday, Slaybaugh's friends and colleagues gathered at the restaurant, which closed for the day, to plan a memorial service.

Slaybaugh, a former George Washington University student who had planned to return to college soon, lived with friends on Harvard Street NW. Neighbors said she had moved in recently.

Repairmen spent yesterday rebuilding the ceiling in time for the theater's first afternoon showing.