After her son was drunk, Unruh said Spacey put his hand into her son's trousers and grabbed him. "But the climate in this country has changed now thanks to the fearless women and all sexual abuse victims who have come forward with their accusations against Harvey Weinstein and other sexual abusers".
She said Spacey invited her son to a party before briefly stepping away to use the bathroom.
The teenager had lied to Mr Spacey about his age, she said, but "whether he was over 21 or not, Kevin Spacey had no right to sexually assault him".
Unruh also claims to have consulted with the local sheriff, who urged her to file a report at the time. "So, OK, it happened 10 years ago", said Talese, who did not seem aware of the subsequent allegations by other young men accusing Spacey of sexual misconduct.
Unruh said the alleged assault occurred in July 2016 when her son, then 18, was drinking and intoxicated at a nightclub on Nantucket, CBS Boston reported.
Variety has reached out to Spacey's reps for comment. A publicist said last week that Spacey is "taking the time necessary to seek evaluation and treatment".
She also said that her son recently filed a police report with Nantucket police, and claimed that a criminal investigation is underway. "Not just for my son but for the many others", she added.
Unruh's attorney said: 'The family member of Heather Unruh met Kevin Spacey on Nantucket Island where Kevin Spacey allegedly sexually abused the family member of Heather Unruh'.More news: Syrian army & allies capture last major ISIS held town in Syria
"An individual has provided information to the Nantucket Police regarding an allegation of an indecent assault and battery", said Tara L. Miltimore, a spokesperson for the district attorney's office. However, she hinted that Spacey had assaulted a woman as she told the paper that Spacey had "plied her with booze".
"My son is anxious, but he is also confident the time to act is now", she said.
She said her son continues to struggle with the emotional effects of the encounter.
On Wednesday, Unruh held a news conference, wiping away tears as she spoke.
Even before those allegations surfaced, Unruh revealed in the midst of the Harvey Weinstein scandal last month that Spacey had assaulted someone close to her.
Shortly after Rapp's allegations, Netflix announced that production of season six for "House of Cards" was suspended. The first, actor Anthony Rapp, accused Spacey of attacking him in a bed when he was 14 more than 30 years ago. Rapp said that he went to watch TV in Spacey's bedroom until after midnight because he became bored.
He said in a statement: 'But if I did behave as he describes, I owe him the sincerest apology for what would have been deeply inappropriate drunken behavior'. Richard Dreyfuss" son Harry called him "a sexual predator' in an article he wrote for BuzzFeed.