At 3:46 a.m. on May 20, a bearded, dark-haired man registered under the name of J.A. Johnson stepped out of Room 763 in the Rockville Ramada Inn, pressed the elevator button, and pulled a Smith & Wesson revolver on two men who ordered, "Drop the weapon; FBI."

Nine days later, that man -- John Anthony Walker Jr. -- stood in handcuffs in federal court in Baltimore, never once looking at his 22-year-old son, Navy Seaman Michael Lance Walker, charged with passing to his father classified documents from the aircraft carrier USS Nimitz.

Tomorrow, John Walker, 48, is expected to plead guilty to espionage and conspiracy in exchange for more lenient treatment for Michael Walker -- the son he allegedly recruited to join a Soviet spy ring. Authorities say John Walker masterminded the ring that also included his brother, Arthur James Walker, 51, who is awaiting sentencing on seven counts of espionage, and his close friend, Jerry Alfred Whitworth, 46, whose trial is set for Jan. 13.

Michael Walker, who one friend said would have "done damn near anything to please" the father he revered, has also agreed to plead guilty, government sources said Friday.

The plea arrangements described by the sources came on the eve of jury selection in the trial of John Walker, a chief warrant officer who held a "Top Secret/Crypto" clearance when he retired from the Navy in 1976 after 21 years of service. Michael Walker's trial was to have started at the conclusion of the case against his father.

It was the latest twist in the Walker family drama, half soap opera, half spy scandal.

The arrests in what authorities have described as the biggest espionage ring since that of Julius and Ethel Rosenberg three decades ago started with a telephone call to the FBI's small Cape Cod office.

Barbara Joy Crowley Walker, making the call on her 47th birthday, said she had been drinking but wanted to pass along a tip: Her ex-husband was a spy.

Barbara Walker acted at the urging of her daughter, Laura Walker Snyder. In an interview this summer with the Christian Broadcasting Network, Laura Snyder said her estranged husband had "blackmailed" her, threatening to expose John Walker if she tried to gain custody of their son.

Terry Heaton, producer of "The 700 Club," which broadcast the interview, said Snyder urged her mother to call the FBI because "as long as John Walker was free, they realized they would never see their son and grandson."

Snyder told the FBI, according to an affidavit, that her father had tried to recruit her as a spy when she was an Army communications specialist stationed in Fort Polk, La., in 1978 and 1979.

But Snyder, who is now working in the biblical studies department of CBN University, said neither she nor her mother ever suspected that Michael Walker might be involved.

"I don't think he [Michael] really understood what he was doing . . . . I know that Michael was manipulated," she said during the interview. "My father tried it with me. I came that close to agreeing to do the same thing . . . to please my father."

But the portrait she painted of her father was the opposite of a man who would risk life imprisonment in exchange for lenient treatment for his son.

John Walker, she said, did not "like me to call him Dad. He likes to pretend that he has no responsibility to his children. He's just this guy I happen to know." Snyder described her father as "arrogant, self-centered, egotistical, sure of himself . . . . He's never called us his children . . . . He called us his little bastards."

In interviews with the FBI before his arrest, Arthur Walker's descriptions of his brother were equally unflattering.

John Walker, he told agents, had "strapped a money belt" on their aged mother to smuggle cash into the United States after a European trip and had urged Barbara Walker to sleep with other men for money when a bar they owned was failing. His brother, Arthur Walker told the FBI, was "the stingiest SOB that ever lived."

According to the FBI report, Arthur Walker "advised that John wanted a 'Godfather type of family,' the 'Mafia type,' where there was loyalty and a 'closed-mouth attitude.' " When Michael Walker joined the Navy, Arthur Walker "knew what was going to happen," he told the FBI.

Arthur Walker described how his younger brother recruited him as a spy during a January 1980 conversation outside Charlie's Waffle House in Virginia Beach, Va.

Arthur Walker was "down in the dumps" about the failure of a radio repair business he and John Walker had owned, he told the FBI, when his brother told him about "friends who will pay for classified information," Arthur Walker recalled his brother saying. John Walker described the friends as "the Russians," Arthur Walker said.

After he obtained a job as an engineer at VSE Corp. in Chesapeake, Va., Arthur Walker told the FBI, "Then the prodding started to get him [John Walker] stuff."

Walker admitted receiving $12,000 from his brother, and he said he returned half to repay their business debts. He said he gave John Walker copies of a training manual on repairing damage to a Navy ship and a report on equipment failures on amphibious vessels.

"I should have said no to him, but I couldn't really. I just couldn't," Arthur Walker said in an interview with The Washington Post the day after his conviction. "He is my brother."

If Judge Alexander Harvey II accepts guilty pleas from John and Michael Walker tomorrow, the remaining defendant in the case will be the only non-Walker accused of participating in the espionage ring: John Walker's Navy shipmate and sailing companion, Jerry Whitworth of Davis, Calif.

According to government sources, John Walker, as part of the plea arrangement, has agreed to testify against Whitworth, whom he met when they served as communications instructors at a Navy training school in San Diego in 1970.

Whitworth is charged with receiving $332,000 from Walker in exchange for classified Navy information, including a manual on contingency plans in the event of hostilities in the Middle East and "key cards" that could be used to decode sensitive Navy messages.

Whitworth's lawyers said that the government is nervous about the strength of its evidence against their client and sought John Walker's testimony to buttress an otherwise largely circumstantial case.

"It's an admission on their part that their case against Whitworth is weak, and frankly I don't think this is going to make it any better," lawyer James Larson said yesterday.

Walker's reported agreement to testify against his longtime friend, Larson said, fits with his "manipulative" character.

In a letter to a former high school teacher in July, Whitworth described the case against him as "a giant misunderstanding" by authorities incapable of understanding the close nature of his friendship with John Walker. Federal agents, he said, "particularly can't accept that I could be a friend of Walker's and not be involved with his alleged activities."

Larson, who is still awaiting the security clearance he needs in order to see the classified documents his client is accused of giving to John Walker, has asked Judge John P. Vukasin to suppress statements given to FBI agents by his client and items seized in a search of Whitworth's mobile home the morning of John Walker's arrest.

A hearing on the motions is scheduled for Friday. In an affidavit supporting the motion, Whitworth for the first time publicly described the scene that morning.

Whitworth said he was "dumbfounded" when the agents informed him of Walker's arrest. Among the questions agents asked him, Whitworth said, was whether he would trust Walker with national secrets. "I said that I would have no reason not to, and they kept probing," Whitworth said.

Before the agents arrived, Whitworth said, he was sitting at his personal computer, "ironically . . . just finishing up a letter to John Walker."