One day in the spring of 1971, a thin, well-dressed and smooth-speaking young man named Ross Fields from Washington walked into Bob Arum's office at Top Rank Inc. in New York with a plan for a piece of the action in the Muhammad Ali-Jimmy Ellis fight.

Arum had never met the young man. But he recalls he was impressed by him, and his plan for closed-circuit telecasts of the July 26 fight in such medium-sized markets as Wilmington, Del., Memphis and Winston-Salem, N.C., made sense. In due course a deal was struck. Top Rank would permit Fields to do the telecasts in exchange for a percentage of his receipts.

He had trouble, Arum recalls, locating Fields and collecting his money after the fight, although he did get some of it. And Fields had a plausible explanation when he met Arum several months later to discuss plans for a similar arrangement for Ali's June 27, 1972 fight with Jerry Quarry.

"He disappeared without paying us on that fight. We never saw him again," said Arum, who figures Fields took him for between $10,000 and $20,000.

Arum had long written off the debt by early 1980, when a new and aggressive Los Angeles-based fight promoter, Harold J. Smith, the president of Muhammad Ali Professional Sports Inc. (MAPS) began to make his imprint on the boxing world, spending lavishly on purses and promotions.

Smith, bearded and portly, rose rapidly in the high-stakes world of fight promotions, and it was only natural for him to call on Arum in the course of putting together a fight.

"I must have met with Harold Smith four of five times. We never did put a deal together but we had a perfectly okay relationship," Arum said yesterday.

Few people were more surprised than Arum when it was revealed in U.S. District Court in Los Angeles Monday that Smith, charged in a lawsuit filed by Wells Fargo National Bank with illegally diverting $21.3 million in bank funds into MAPS accounts, and Fields are the same person.

"I was stunned," said Arum. "As soon as I heard the name Ross Fields, I went to our files and there it was. They were so different. Like day and night.

"The first guy was skinny, clean-shaven, smooth-talking con artist. The second guy was burly and bearded, affable and very laid-back. Ross Fields was always a very spiffy dresser. Harold Smith always wore Western clothes and hat.

"He must have been laughing up his sleeve all the time. I didn't know who he was, but he must have known who I was. I haven't changed all that much."

Fields, 37, is currently being held in lieu of $400,000 bail in Los Angeles on charges of falsifying passport information, forgery and false pretenses. He was described in court by federal prosecutors as a "fugitive bad-check and bunco artist" who left a trail of 100 bad checks in 30 states while he was crossing the country with his wife between 1973 and 1974.

A former student at American University, which he attended on a partial track scholarship, Fields was a fight and concert promoter in Washington. He owned and operated the Sammy Davis Jr. Discotheque at 13th and E streets NW before leaving town in the early 1970s.

A native of Birmingham, Ala., Fields grew up and attended schools in Huntsville, Ala. His former track coach, Jerry Davis, remembers him as a "hard-working, quiet, reserved young man with a great deal of leadership ability.

"He came from a low economic family, and without the track scholarship he would not have been able to attend any university," said Davis, who is godfather to Fields' son by an earlier marriage. "He was never in any trouble."

Davis, now a high school principal in Huntsville, recalls being asked by American University to recommend Fields for a scholarship. "I told them I had nothing but the best kid of recommendation, but that he had no money. He would need everything they could give him."

According to Davis, Fields' goal in life was to make the U.S Olympic track teams, but after he arrived at American University he became interested in promoting events -- first concerts on campus and later other, larger events.

More recently, as the chairman of MAPS, Fields was generally respected in the fight-promoting community.

"It was always a delight to deal with Harold Smith because he always paid off right away," said Jim Jacobs, the manager of fighter Wilfred Benitez.

"He seemed delightfully frank and out front. If everybody paid their bills as quickly as Harold did, this business would be much easier." CAPTION: Pictures 1 through 3, Bob Arum says he never suspected Harold Smith was Ross Fields. Fields, now 37, is currently being held in Los Angeles in lieu of $400,000 bond. Photos by UPI and The Washington Post