On March 17, Lynn Largent made one of his regular excursions to Charles Town and enjoyed a successful evening. He split a winning ticket on the Big Exacta and left the track several hundred dollars ahead.

Willie Logan's fortune that night was quite the opposite. He lost all of his meager bankroll and had to borrow money to get back home to Alexandria.

To both men, it had seemed a routine night at the races. Neither could have imagined that it was a night that would alter their lives.

But as a result of a chain of events at Charles Town, Largent and Logan find themselves in bewildering, almost terrifying situation. Both stand accused of felonies when they say they did not commit. And when they go on trial Monday in Martinsburg W.Va., they face possible three-year jail sentences if convicted.

During March, Internal Revenue Services agents were swarming over Charles Town. They were hunting for ten-percenters, men who cash big winning tickets for a fee so the real winners can conceal their identities from the IRS. One of the suspects the agents were watching was Michael H. Cohen, known to all the habitues of the Charles Town clubhouse as "Heavy."

Largent, a produce broker in Winchester, Va., was oblivious to all this activity on March 17. He was intent on trying to win the Big Exacta, the gimmick requiring a bettor to pick the one-two finishers in the fifth and sixth races. Largent came out of the fifth race with one live ticket, but he could not decide between the 4-6 and 6-4 combinations in the sixth.

So he sought, and found another bettor with a live ticket who was willing to form a partnership with him. Largent didn't know the old man's name, but they had a nodding acquaintance and together they played 4-6 and 6-4.

When the 6-4 combination won, the men shared a ticket worth $846.40. Under IRS regulations, the winning ticketholder must fill out a tax information form to collect his money. Largent's partner volunteered to cash it, saying he was 72 years old and didn't pay any taxes anyway. He handed over half the proceeds to Largent, who wrote in a notebook (where he records all his racetrack transactions) that he had won $423,20 on the Big Exacta.

After collecting his money, Largent saw Heavy standing by a television monitor, and remembered that he had borrowed $20 from him on a previous night. Largent walked over and unceremoniously handed him a folded-up bill.

As he did, the IRS agents were watching. They had seen Heavy at the Big Exacta cashier's window that night. They assumed he was ten-percenting tickets for other horseplayers. And they concluded, from the transaction they witnessed, that Largent must be one of those people.

He was not, but the old man who did cash the ticket for Largent (in a completely legal fashion) hasn't been seen at the track in months. And Largent still does not know his name. So he finds himself charged with "causing the preparation and presentation . . . of a document, to wit, Statement for Certain Gambling Winnings . . . which was fraudulent and false . . . in that the name of the recipient of the income . . . was falsely stated, misrepresented and concealed."

Though Largents plight is frightening, he at least has $423.20 as a slight consolation for all his woes. Willie Logan doesn't even have that. He did not play the Big Exacta on March 17, let alone win it. Nor did he win anything else.

Logan, went broke, but he was so worried, because he knew he was in a congenial environment.

"Everybody's friendly at the track he said, "and so at the end of the night I asked a guy if I could borrow $5 from him."

The guy was Heavy. The IRS agent watched as he handed Logan the money, and apparently thought the were seeing part of a ten-percepting transaction, for which Heavy was indicted. He will stand trial along with Logan and Largent.

Heavy had cashed four Big Exacta tickets, and the agents wanted to line those tickets to their real owners in order to make their case.

Three weeks later Logan was at Charles Town again when the IRS men approached him, took him outside, accused him of turning over Big Exacta ticket to Heavy and asked him to testify against the ten-percenter.

Logan told the agents just what has happened that night, but the agent chose not to believe him. This week he and Largent can only hope a jury of their peers will be more receptive to their account.

"The grand jury evidently felt there was enough evidence for an indictment," said Stephen Jory, who is prosecuting the case. "If they are convicted, so be it."