Frank Wills, 52, a security guard who played a brief but decisive role in detecting the break-in at the Watergate office complex that eventually led to the resignation of President Richard M. Nixon, died Sept. 27 at a hospital in Augusta, Ga. He had a brain tumor.

Mr. Wills, a Savannah, Ga., native who left high school to join the Job Corps, came to Washington on a visit in 1971 and decided to stay. That year, General Security Services hired him for the midnight-to-7 a.m. shift at the Watergate.

On June 17, 1972, he was about an hour into his shift when he spotted a piece of adhesive tape on a door between the basement stairwell and the parking garage. Suspecting that the cleaning crew had taped over the door latch to prevent it from locking, Mr. Wills removed the tape and went on his way.

During a later inspection, he discovered new tape and called D.C. police, who found five men in the sixth-floor offices of the Democratic National Committee. Some of the burglars, who were wearing surgical gloves and carrying bugging equipment, were former CIA personnel.

The break-in eventually was linked to the White House and resulted in charges including conspiracy and obstruction of justice. Nixon resigned in August 1974.

During the investigation, Mr. Wills, whose salary was $80 a week, was sought out by news organizations. He hired Washington lawyer Dorsey Evans to represent him and charged honorariums of up to $300 to do interviews. Several reporters paid the fee, but Mr. Wills's plan to work the lecture circuit never coalesced.

He received awards from the Democratic Party and the Southern Christian Leadership Conference, which bestowed on him its highest honor, the Martin Luther King Award. He also played himself in the 1976 movie "All the President's Men," based on a book about the Watergate scandal written by Washington Post reporters Bob Woodward and Carl Bernstein.

But Mr. Wills came to speak bitterly about never successfully cashing in on his contribution to the Watergate saga.

In 1973, he left the security company, citing the lack of paid vacations. When he could not find steady work after that, he told The Post: "I don't know if they are being told not to hire me or if they are just afraid to hire me."

By the late 1970s, he was in North Augusta, S.C., living with his ailing mother. He worked the late-night shift as a guard at Medical College of Georgia and sold a diet formula marketed by comedian-activist Dick Gregory.

In 1983, Mr. Wills was sentenced to a year in prison for shoplifting a pair of sneakers from a discount store in Georgia. In recent years, he mowed lawns and did other odd jobs for elderly neighbors, and he often rode around town on his bike.

Mr. Wills was considered a forgotten figure of Watergate when, in 1997, came a deluge of interview requests on the 25th anniversary of the break-in. He emerged embittered, telling a Boston Globe reporter: "I put my life on the line. I went out of my way. . . . If it wasn't for me, Woodward and Bernstein would not have known anything about Watergate. This wasn't finding a dollar under a couch somewhere."