Henry J. Blackwell and Bible-toting Father Robert Graham met at Dulles International Airport five years ago with a Mexican Businessman to arrange an investment deal for their religious organization.

Since that meeting the business has never been seen and he may have been disembered and dumped in the Cheseake Bay. But his body has never been found. The minister, Blackwell and the religious group were all bogus.The investment deal was part of a scheme, Harvard Ph. D. Kenneth B. Krohn, alias Blackwell admitted yesterday in a signed statement to retrieve $120,000 he said the businessman swindled from him.

Yesterday Krohn pleaded guilty in U.S. District Court in Alexandria to conspiracy to extort money from the businessman and travelling across state lines to aid racketeering U.S. attorneys dropped two kidnapping charges against Krohn.

Thurston Drew Shrader, who acted as Father Graham at Dulles was an unindicted coconspirator in the case. Shrader pleaded guilty last June to misprison of a felony, meaning that he failed to notify authorities that a crime had been committed.

The case which has been elements of a detective thriller began in 1972 when Krohn loaned Mexican businessman Raul Hernandez - Bustamante $120,000 to invest for him, according to U.S. Attorney William B. Cummings.

Hernandez pledged property as collateral for the loan, Cummings said without telling Krohn the property had been used as collateral for another deal at the same time. Consequently the deal went sour, Cummings said.

Krohn then went to Mexico where he filed a suit against Hernandez to get the money back, Cummings said. Hernandez had some of his friends rough him up a little and throw him in jail, the prosecutor said.

Krohn managed to get out of the jail and came back to the United States where he promptly began devising a scheme to get revenge on the businessman and recover his investment, Cummings said.

Krohn and Shrader, whose sister Krohn dated, set up a fictitious religious organization. Shrader, using the alias of Father Graham called Hernandez on Dec. 20, 1972, saying he sum of money for the religious group wanted Hernandez to invest a large, After several attempts to get him to come to Dulles, Hernandez agreed, but only if his business associate, who would also act as a bodyguard, came along.

Hernandez arrived at Dulles on Jan.20, 1973, about half an hour earlier than his business California business associate bodyguard. Hernandez had been told by "Father Graham" that the representative of the religious group at Dulles would be a minister carrying a Bible under his arm, Cummings said.

Meanwhile, Krohnrented an Avis car in the name of Campbell and he and Shrader drove the businessman in the car to a rented apartment in Severna Park Md.

At the apartment, Krohn forced Hernandez to write letters to his family and business associates asking for money, at least, $120,000 to be sent to Blackwell, who really was Krohn, Cummings said. The money was subsequently delivered to Krohn, Cummings said.

After that, Cummings now says, "no one knows what happened."

Shrader, who hid behind for aliases in the last four years, said earlier that he helped Krohn because while Krohn was in Mexico he had been using Krohn's identity to teach computer science at Seven Prep School in Seven Park.

Shrader told The Post that he went to the Severna Park apartment several days after the airport rendezvous, and saw what he was told was Hernandez's head in the bathtub. The teeth, he said, were in the sink.

Shrader said he then dump what he believed eo be Hernandez's body off the Cheaspeake Bay Bridge after his life and that of his girlfriend was threatened.

There has never been any proof that a murder was committed, Cummings said yesterday.

When Shrader was arrested last summer in Newport News. Va., he was posing as T. Alexander Marbury, a history teacher and popular basketball coach at a Newport News High school.He is now serving a three year prison term.

Krohn's attorney, George West, said yesterday that neither he nor Krohn would comment on the case. They earlier have disputed Shrader's account of the case.

Krohn is scheduled to be sentenced Nov. 18. The maximum penalty for each of the charges he pleaded guilty to is five years in prison.