It was just an ordinary party back in 1974, said Thurston Drew Schrader as he sat with his hands neatly folded and handcuffed in the U.S. marshal's office in Alexandria recently. And he asked the usual questions of the man he met there - occupation, naturally, and education, the degree with which he had graduated.

But what Schrader's party acquaintance didn't know was that the answers provided Schrader with the means to establish yet another in a series of four assumed identities. Those identities enabled Schrader, a college dropout, to get eight teaching jobs, and as he tells it, made him the unwitting dupe of a bizarre kidnaping, murder and mutilation of a Mexican businessman here four years ago.

Schrader was arrested in Newport News recently and is being held without bond in Alexandria city jail. He is charged with kidnaping, conspiracy, making false statements and obstruction to justice in connection with the 1973 disappearance of Raul Hernandez, a Mexican businessman. While a Schrader contends that Hernandez was kidnapped, murdered, dismembered and disposed of in various parts of Chesapeake Bay, his body was never found.

Last week, Schrader agreed to talk about his penchant for other people's identities and how it led to his involvement in the case.

Two weeks ago, Schrader was T. Alexander Marbury, a history teacher at Peninsula Catholic High School in Newport News, popular basketball coach who had led the school's team to its first winning season in a decade, Big Brother to disadvantaged boys, a respected member of the community.

The lines between fact and facade had become so blurred in his mind, Schrader said, that it seemed to him that it was as Schrader that he had been the impostor, and that as Marbury, his life had finally begun to assume some reality.

But while it was T. Alexander Marbury who was helping out the girls' softball team one sunny afternoon at the behest of a local businessman in Newport News, it was Thurston Schrader whom five carloads of FBI agents came to the softball field to arrest.

The real Thomas Marbury had received a tuition bill for classes Schrader had taken under Marbury's name at Radford College. The real Marbury called the police, and Thurston Schrader became himself again.

Now Schrader sits in isolation in jail, held without bond in a four-year-old case that federal authorities call one of the most complicated they have ever encountered.

As Schrader tells his story, however, the complexities of the case seem simple beside the tangled threads of his life story.

The son of a Navy chaplain and a mother who committed suicide when Schrader was nine years old, Schrader said his life as an impostor was born out of practical considerations. Forced to quit the University of Maryland after his freshman year because of lack of funds, Schrader was heavily in debt and working as a Virginia highway inspector in Leesburg when he read a newspaper article that seemed to offer a way out.

"I read this story about how easy it was to get somebody else's college transcripts," Schrader said. "I knew it was wrong, but I thought if I could get the transcripts and get a teaching job for a couple of years, I could save enough money to go back and get a degree of my own."

And besides, Schrader said, "my father always told me I would never amount to anything. I figured if I could pass myself off as a teacher, I could prove I could be a success."

It was only a matter of thumbing through a University of Maryland yearbook, picking out a graduate who bore a vague physical resemblance to Schrader and then writing the university for that man's transcripts and placement records, Schrader said, and get him started.

Then, as "Philip Schroeder," Schrader got a job teaching biology at Northeastern Senior High School in Anne Arundel County in 1968. "I'd never even dissected a frog before," Schrader said, "But I found I had a knack for teaching. Every night I would go home and read enough to get me through the next day's lesson."

Officials at both the University of Maryland and the University of North Carolina (to whom Schrader wrote for the transcripts that established him as T. Alexander Marbury) confirmed that there is little they can do to be sure that the person to whom they are sending the records of grades and degrees is actually the person who earned them.

Although most universities prefer that an alumnus writing for his transcripts include his social security number with his request, University of Maryland Director of Registration William Spann acknowledged that the transcripts could be sent if a person simply noted the degree received and the year graduated, information that could easily come from a college year-book or a cocktail party conversation.

Since the university fills over 60,000 requests for transcripts a year, Spann said, there is "no way" of verifying signatures. "The assumption is that they're honest," he said.

Buoyed by his success as a biology teacher, Schrader said, he next taught advanced placement physics at Florida Military Academy, but was lured away in 1971 by a job offer from the Bartram Girls' School in Jacksonville, Fla. "They wanted me to live on campus with all those beautiful women," Schrader said. "I culdn't resist." Bradford Lamson, the school's headmaster, confirmed that Schrader had taught advanced placement chemistry and physics at the school. "It's possible to get flim-flammed, doggone it," Lamson said. "I guess it happens in the best of families."

Meanwhile, Schrader had met Kenneth B. Krohn, a Harvard Ph.D. and computer expert who was dating Schrader's sister, Heather, at the time and who is now listed as an undicted coconspirator in the 1975 grand jury indictment.

Thus, when a girl Schrader had fallen in love with at Bartram decided to go to college near Baltmore, and Schrader discovered that Krohn and his sister had left from Mexico, Schrader decided it was time for a change.

Helping himself to Krohn's credit cards and credentials, Schrader got a job teaching mathematics and computer science at the elite Severn Prep School in Severna Park. Learning how to use a computer was easy, Schrader said, compared to the task of explaining to his girl friend how Philip Schroeder was actually Dr. Kenneth Krohn.

In the fall of 1972, Schrader said, Krohn returned and discovered the identity problem. Schrader and Krohn both said that Krohn agreed to let Schrader continue with the masquerade on condition that he leave the job at the end of the school year.

Meanwhile, Schrader said, Krohn had other things on his mind than the theft of his identity.

Krohn, Schrader said, told him that while in Mexico he had been "ripped off" in a land deal by a Mexican businessman, Raul Hernandez, and asked Schrader's help in luring Hernandez here from Mexico. Schrader said, Krohn told him Hernandez would then be arrested by the authorities.

"I said I'd help him out. Schrader said. "I didn't see anything wrong with it, and besides, I was using his namea, after all."

Using the name of Robert Graham, Schrader said he placed several calls to Hernandez telling him he wanted to invest money and asking the Mexican businessman to meet him in Washington. On Jan 20, 1973, Schrader said he accompanied Krohn to Dulles Airport, where Schrader said he thought Hernandez was to be arrested by federal authorities.

But, Schrader said, Krohn emerged from the airport only to tell him that Hernandez had actually been arrested while changing planes in Dalles.

The following Tuesday, Schrader said, Krohn asked him to come to his Severna Park apartment, where, he said, he was confronted by the head of Raul Hernandez in the bathtub. The teeth, he said, were in the sink.

Also in the apartment, Schrader said, were several plastic bags and a green foot locker that Krohn told him contained the rest of Hernandez.

Schrader said he then helped Krohn dump the body over the Chesapeake Bay Bridge after Krohn threatened his life and that of his girl friend.

Krohn, however, denies Schrader's account entirely, claiming that the last time he saw Hernandez was in Mexico. In addition, Krohn said in a long-distance telephone interview from Cambridge, Mass., a Mexican acquaintance of Krohn told him he had actually seen Hernandez a year-and-a-half after the alleged murder and Hernandez was sipping tea in a Buenos Aires cafe.

"I wish Thurston would stop saying these things about me," Krohn said. "People sometimes cross the street to avoid talking to me."

Both Krohn and Schrader have been arrested twice in connection with Hernandez' disappearance, not counting the time Schrader was arrested because federal authorities thought he was Krohn. Krohn was arrested a second time in 1974, only to have an Alexandria magistrate dismiss the charges for lack of evidence.

Krohn is now living in Cambridge and suing the government for the return of possessions seized in a 1974 search of his apartment.

Schrader said that following his release in 1973, he taught at Albany State College in Georgia under Krohn's name, in a District of Columbia high school undet the name of a colleague he met at Albany State, attended Radford College under the name of T. Alexander Marbury, and taught history and government in Bedford County, Va., under that name before going to Peninsula Catholic High School in Newport News in August, 1976.

In Newport News, Schrader said, "Thurston Schrader to me was gone. I'd look at my friends who had wives and kids to come home to at night, and that's what I wanted for myself. I know how that I could be a success. I've been successful at everything I've tried."

Now, said Thurston Schrader, "I'd just like to file my income tax under one name like everybody else."