When Betsy Chase, 21, of Sterling and her 18-year-old sister, Whitney Chase, flew to an exclusive Detroit suburb for a brief holiday visit with their mother and stepfather, they had planned to go ice-skating, shopping and out to dinner.

Instead the two sisters wound up as central figures in what Michigan law enforcement officials say was a convoluted series of events that sprang from their mother's concern over their fundamentalist religious beliefs and ended with an aborted scheme designed to extort $5,000 from their father, a prominent Washington lawyer.

The two young women, members of a born-again Christian church in Northern Virginia, were back in Washington yesterday where they joined their father, Georgetown attorney Anthony Chase, in recounting the events that led authorities to arrest their mother, stepfather and eight others on kidnaping charges. Two were also charged by the FBI with extortion in what one agent described in typical understatement as "an unusual case."

"The second night my mother said we were just going to their old house to pick up some furniture and then out for a casual dinner," recalled Betsy Chase. "But when we got inside the house there were all these people there and my mother said: 'Betsy and Whitney, we're not going out to dinner. We want you to talk to these deprogrammers.' "

Betsy Chase said she and her sister initially agreed to talk to the deprogrammers who authorities said were hired by their mother, Karen Larson.

"But then they had me go to an upstairs bedroom and Whitney went down to the basement and they showed us movies about the Moonies and Jim Jones. I wasn't allowed to see my sister or call anybody and there were guards everywhere."

Chase said neither she nor her sister was physically harmed during their four days in the Bloomfield Township home rented by their mother and stepfather, Robert Larson, 48, president of the Taubman Co., an international shopping center developer. The sisters regularly were fed chili and lasagne prepared by their mother's cook, they said.

Police and FBI agents surrounded the house on New Year's Eve and arrested the Larsons and eight others after one of the men guarding Betsy Chase allegedly tried to extort $5,000 from the girls' father, an FBI spokesman said.

Betsy Chase said one of her guards had "started being friendly with me and telling me what was going on with Whitney. And then he asked about my dad's money. First, he planned to ask my father for $3,000 but when he found out he was a lawyer, he changed it to $5,000," she said.

Chase said she gave a man her father's telephone numbers. On Dec. 30, Anthony Chase said he received a collect call from a man who identified himself only as "Larry."

"He told me he was an armed guard and some people were holding my daughters at a remote location and if I wanted to see them again in a reasonable period of time I should deliver a package containing $5,000 to 'Larry' care of 'Laurie' at an address in Minneapolis," Chase said in an interview at his Georgetown law office.

Chase said he secured the money and then called the FBI.

On New Year's Eve, FBI officials say they arrested a women identified as Laurie Atringer, 32, in Minneapolis. Shortly afterward, authorities converged on the house where the girls were allegedly being held and freed them. Among those arrested was Atringer's 25-year-old brother, Larry Leon Iron Mocassin, who is charged with extortion.

Yesterday a state prosecutor in Michigan said he wanted to investigate the case, other lawsuits involving religious cults and the Northern Virginia Bible school the women attend before deciding whether to press the kidnaping charges. That decision does not affect the federal extortion charges.

"Their mother said she had made an extensive study of cults and was concerned because she felt they were manifesting personality changes and believe in faith healing," said prosecutor Richard Thompson. "We want to talk to local authorities about cults and do some research before making a decision [whether to prosecute]."

The School of the Prophets, which the sisters attend, is a branch of the Assembly of God denomination and part of Sterling's Calvary Temple. Its founder, Pastor Star Scott, said he was amazed anyone would consider it a cult. Scott, who hosts a weekly radio show called "Sword of the Spirit", added: "Besides you can't deprogram a Christian. It's not a psychological thing, it's a spiritual thing."