Much of her life, Geraldine Williams was an invisible servant to others, wiping clean their dirt, scrubbing their floors, emptying their trash.

She cleaned the houses of those who can afford to have others take care of their domestic chores. For 15 years, she cleaned three office and academic buildings on the campus of University of Massachusetts at Lowell.

Co-workers said Williams left surfaces spotless. Friends and neighbors say she brought the same energy to helping others, from senior citizens she ferried to and from doctor appointments to a neighbor whose vacant lot she helped mow.

After Williams retired from her janitor's job a couple of years ago, she didn't stop cleaning private houses, earning extra money to pad her pension. Friends described Williams, who took home a check yesterday for more than $117 million, as a vigorous worker who seems younger than her 67 years.

This week, luck and infinitesimal odds conspired to turn the former custodian into a millionaire many times over. And the woman who spent decades doing often-overlooked work took center stage as she accepted the largest lottery jackpot in state history.