A 39-year-old woman has been arrested and charged with killing her 71-year-old landlady, a longtime psychiatric social worker who has been missing from her home in the Chevy Chase area for several days, Montgomery County police said.

After a dispute earlier this month with tenant Susan Lynn Sachs, the therapist, Joyce Hadl, told police that Sachs needed psychiatric help and asked that she be evicted, according to a statement filed by police in county District Court.

No body has been found, and police said they were searching last night.

In a statement filed Monday to support a charge of first-degree murder against Sachs, police said that Hadl's mattress appeared to be stained with blood and that Sachs had been seen leaving the house on Washington Avenue about 3:30 a.m. Saturday with garbage bags filled with unknown items.

Police also said in the statement that they had found receipts for cleaning supplies recently purchased by the suspect. They said Sachs told them she had scrubbed the floor in Hadl's room in the house, located just east of Rock Creek Park.

Police said Sachs had given them an inconsistent statement about her interactions with Hadl. Sachs was being held last night at the Montgomery County detention center.

According to police, a cousin who had expected to meet Hadl on Saturday became concerned when he could not find her at the house, which is on a three-block street tucked into a right-angle bend of the park and just south of East West Highway.

The cousin eventually called police.

After forcing open a door, police said in the statement, they found Hadl's bed without sheets. A new mattress cover had been placed on the bed, they said, but beneath it they found what they described as a dark stain about a foot and a half wide.

In the sworn statement setting out evidence for Sachs's arrest, police described the stain as being consistent with blood.

On Thursday, police said, a note had been found on the door of Hadl's house. The note said Hadl had an emergency and would not be seeing patients, but police said they were told that it was not in Hadl's handwriting. Witnesses also said that Hadl's car remained at her house.

According to police, at least three boarders lived in Hadl's residence, a brick house that stands at the top of a long flight of steps set into a gently sloping lawn.

On Aug. 16, the day one of the boarders said he had last seen Hadl, officers had gone to the house in response to the report of a dispute there, the affidavit said.

At the house, police said, Hadl told them that Sachs "was in need of psychiatric help."

Police said that Hadl wanted Sachs evicted but that Sachs refused to go, and officers said that they were without legal power to force her out.

Police were called Saturday. A cousin, Neil Goldstein, said that he had expected to meet Hadl at her house at about noon to go to the Legg Mason tennis tournament in the District but that she could not be found.

As the hours passed, he "cleaned the porch and raked the leaves," in part to help pass the time, while waiting for his cousin. He said he did not leave until midnight.

Police said they were told that Hadl had missed appointments and had not returned relatives' telephone calls.

A neighbor who declined to be quoted by name said that "nobody in the neighborhood had any idea of anything going on."

Goldstein described Hadl, a native of Boston, as a "wonderful person" who had come to this area about 40 years ago and had "a large following" in her practice as a psychiatric social worker.

She "wanted to help people" and was good at talking to people about their problems, Goldstein said. A neighbor said he understood that she treated clients at home.

Hadl had many interests and volunteered as a tour guide in the Washington area, the cousin said.

According to the cousin, she was divorced, with grown children living in the Washington area.

Hadl is listed on the Maryland Board of Social Work Examiners' Web site as having received a license in clinical social work in 1977. An Internet site indicates that she practiced at one point in a building on Connecticut Avenue NW, near the National Zoo. Police could not provide further information last night.