The disappearance of a woman from the Rockville Nursing Home four months ago has left nursing home officials and city police baffled, with neither having any clues on her whereabouts.

Police said Vivian Heaton, 73, a seven-year resident of the nursing home at 303 Adclare Rd., disappeared without a trace about 8:15 p.m. June 24, minutes after she told nursing home staff members that she was going out for a brief walk.

Staff members said they noticed that Heaton was missing about 15 minutes later when she failed to return.

"It's like beating a dead horse," Rockville police officer Rich Tepper said of the investigation. "I've tried everything I could think of. You name it, I've tried it."

Nursing home administrator Ray Cromwell said that Heaton, a manic-depressive who was under medication, often was permitted to take short walks along the nursing home grounds. Most of the time on these walks she was visible to staff members inside the building, he said.

Cromwell said Heaton was capable of feeding and taking care of herself, and that she did not suffer from disorientation or any degenerative loss of memory.

Officials of the nursing home, which opened in 1977, said that no other resident has disappeared from the home for even a few hours.

"The staff is really upset about it. We're all concerned for her safety and well-being and hope that she comes back," said Cromwell, adding that the nursing home is offering a $1,000 reward for information leading to Heaton's safe return.

Heaton, a frail widow with salt-and-pepper hair, was wearing a pink dress, a white sweater and sandals when she disappeared, Tepper said. She had neither money nor belongings with her, nursing home officials said, so they assumed that she had not wandered far. But weeks of searching the building, grounds and nearby woods, by staff members and several police agencies, yielded no clues.

Police said that Heaton has a niece in Laurel and a sister in Virginia, but that neither has seen or heard from her.

Heaton seemed content at the nursing home, officials said, and she did not express any desire to leave.

"That's what has amazed me through this whole thing," Tepper said. "I don't understand it. I've talked at length to people at the nursing home, and there's no doubt in my mind she got along with them real well."

Despite the length of the investigation, Tepper said he believes that Heaton has not run up against foul play.

"She did have psychological problems, but she was lucid," Tepper said. "She knew how to take care of herself. There's a possibility that foul play is involved, but as a law officer, I have to look at facts. And I don't have any facts that substantiate that that has happened.

"I just have this gut feeling she's around somewhere. I could be completely wrong. But until somebody produces a body and we match it up, that's what I'm going to say."