A woman returning to her car from a grocery store at the Wheaton Plaza Shopping Center was abducted by a stranger, raped, bound and gagged, and then thrown about 35 feet into the frigid water of the Patuxent River but was able to swim to safety, Montgomery County police said yesterday.

The 30-year-old Silver Spring woman, whose name has been withheld by police, was in satisfactory condition yesterday at a Montgomery County hospital after her abduction late Monday night. She told police that after being dropped from the Rocky Gorge Bridge, she swam on her back to the shore and then walked to Rte. 29 where a passing motorist picked her up, drove her to the Burtonsville, Md., 7-Eleven store and called police from a pay telephone.

Arrest warrants were issued by Montgomery County police for Richard Dale Baumgartner, 25, of Clarksville, Md., charging him with rape, kidnaping, auto theft and attempted murder in the case. Investigators focused on Baumgartner after his truck was found in the parking lot where the woman was abducted about 10 p.m. Monday, police said.

"Without question, this is one of the most brutal and sadistic crimes we have had in the county in a long time," said Montgomery County Police Chief Bernard D. Crooke. "It is right up there next to a couple of murders we have had."

Crooke said that it is "imperative" that the suspect in the case be arrested as quickly as possible "for the action he took last night -- he is a man without any conscience."

The attacker is believed to have driven off in the woman's car, police said. The vehicle, a brown 1980 Honda Accord, was found at 10:30 last night at the same shopping center parking lot where the woman said she was abducted. Police said they believe it was driven back to the lot last night because the muffler was still warm.

The woman's attacker "was a stranger to her," said Detective George G. Neville Jr.

Baumgardner, the suspect, was convicted in 1978 on two charges, including a sex offense in Howard County and a narcotics offense in Washington County, police said. He was sentenced to 10 years and 3 months in prison, police said. The records show he was paroled in August 1984 from the Maryland Correctional Training Center.

Monday night's attack began after the woman had been shopping at the Giant Food store at Wheaton Plaza, Neville said. "She left the store and was getting into her car when she was abducted at knifepoint."

The man forced the woman into her car and drove her to the Howard County community of Elkridge where he rented a room at the Executive Motel, police said. They said the man kept the woman at the motel about two hours. During that time, he bound and gagged her and raped her, police said.

Investigators would not divulge details of what was used to bind and gag the woman, when she was bound or where the woman was while the man checked into the motel, but one officer said, "She was a captive the entire time."

Yesterday afternoon, while Howard County police were examining the motel room, a motel employe said in a telephone interview that about half of the 26 rooms in the Executive Motel were rented Monday night.

The employe also said the motel worker on duty at the time of the rape did not notice anything unusual about the man who rented the room. Motel employes didn't know what had happened until police appeared yesterday and began asking questions and checking the room for evidence, the employe said.

Neville said that the man and the woman left the motel about midnight and returned to Montgomery County. "At about 1:30 a.m., he dropped her from the Rocky Gorge Bridge into the Patuxent River," Neville said. "Her hands were bound behind her back and she was gagged when he dropped her. Then he drove off in her car."

The woman, who was clothed, managed to swim to the shore of the river, which at that point is part of the Washington Suburban Sanitary Commission's T. Howard Duckett Reservoir, which provides drinking water for Montgomery and Prince George's counties.

WSSC representative Marjorie Johnson estimated that the drop from the bridge to the water is 35 feet. The water under the bridge is 40 to 50 feet deep, she said, and the distance from one side of the river to the other at the Rocky Gorge Bridge is about 225 to 250 yards.

The temperature at 1:30 a.m. Tuesday was 30 degrees Fahrenheit in Montgomery County, according to Weather Service forecaster Robert Oszajca. He said the temperature of the Patuxent water probably would have been 33 to 34 degrees. It was unclear how long the woman was in the water.