Oona Sperr, a New York interior designer who says she gave up her career and spent a decade managing Sid Bass's lavish households, is now suing the 84-year-old Texas billionaire for at least $400 million, claiming he tossed her aside for another woman after years of broken promises.
Sperr filed her federal complaint in Manhattan federal court on Monday, naming both Bass and art adviser Althea Viafora Kress as defendants. The suit accuses Bass of reneging on oral promises of lifelong financial security and shared ownership of their homes, and accuses Viafora Kress of tortious interference, deliberately inserting herself into the relationship and isolating Bass from the people around him.
Bass, described in the complaint as a billionaire at least four times over, has not publicly responded. The New York Post reported it sought comment from Bass, Viafora Kress, and a third woman named in the suit, Patricia Zohn Pfeiffer. None responded.
The lawsuit paints a picture of a man who has cycled through marriages and relationships with a consistent pattern: make promises, extract loyalty, then discard the woman when someone new appears. Sperr's attorneys call it "the latest chapter" in Bass's history of "marriages, divorces, and repeated infidelities."
The complaint traces the relationship to January 2014, when Bass allegedly invited Sperr to move into his Manhattan townhouse over lunch. His pitch, according to the filing: "How about you never leave?" Sperr says she accepted, abandoned her interior design career, and spent the next decade managing Bass's properties, traveling with him around the world, and caring for him through serious health problems.
She called their shared world "Bass Land", a lifestyle that stretched across Manhattan mansions, a ranch in Colorado, a Gulfstream jet, and the Bass family's 21-mile-long private island off the Texas coast, San José Island. Bass allegedly referred to Sperr as "Mrs. Bass" when they traveled and bought her a 25-carat diamond for $2.1 million, sized for her left ring finger. He also allegedly gave her a 20-carat emerald worth $1 million.
Then came the morning of September 3, 2024. Over breakfast at their home in Pagosa Springs, Colorado, Bass allegedly told Sperr flatly: "I want a separation. You are to pack and leave."
Sperr says she asked whether another woman was involved. Bass, according to the complaint, "vehemently denied" it. He allegedly offered a $50 million breakup package, a Manhattan home, another property, continued household staff, and care for Sperr's 96-year-old mother.
That offer did not last.
In the weeks after the September 3 announcement, while Sperr was still packing up at the Colorado home, she says she overheard Bass talking on his headphones to Viafora Kress. She claims she heard him call Viafora Kress "sweetheart" and tell her, "You're my gal!" The two were allegedly discussing Viafora Kress moving into the Colorado home just days after Sperr's departure.
Viafora Kress allegedly demanded that Sperr's possessions be removed, that Bass stop speaking directly to Sperr, and that he not drive Sperr to the airport. Bass drove her anyway, on September 30, 2024, described in the complaint as the couple's last day together.
Less than a year later, on August 9, 2025, Bass allegedly married Viafora Kress at the family compound on San José Island. Sperr says she learned about it on August 22, 2025, when she received a six-sentence email from Bass's account with the subject line "News." The complaint alleges Bass neither wrote nor sent the email, that Viafora Kress used his account to announce her own marriage to him.
The initial $50 million offer evaporated. In its place, the complaint describes a proposed "Maintenance Agreement" that would have paid Sperr $5 million annually for 10 years, given her tenancy, not ownership, of a Manhattan home, and stripped away other benefits Bass had originally promised. For a woman who says she spent a decade running a billionaire's life on the strength of his word, the retreat was the final breach.
Sperr's attorney, Robbie Kaplan, framed the case bluntly in a statement:
"Sid Bass is a billionaire at least four times over. Oona is the woman who spent a decade making Sid's life convenient, abandoning her career, managing their shared homes and affairs, caring for him through his serious illnesses, all because Sid agreed that he would take care of her and her 96-year-old mother no matter what."
Kaplan added that Bass "abruptly ejected Oona, breaking his promises to her," and that Sperr, now 64, "had no choice but to bring this case."
The lawsuit goes beyond the breakup itself. It alleges Bass suffered at least three mini-strokes and that in 2019, a doctor told Bass and Sperr that a brain scan showed abnormalities consistent with what the physician described as "a particularly pernicious form of Parkinson's disease." During the pandemic, according to the complaint, Bass's drinking increased to as much as two bottles of wine on most days, and Sperr observed changes in his judgment, temperament, and memory.
The filing also describes what Sperr's lawyers characterize as a lifelong pattern. Bass and his second wife, Mercedes Tavacoli Kellogg Bass, allegedly began their relationship in the 1980s while both were married to other people. His first marriage to Anne Hendricks Bass, who died in 2020, unraveled in the process. The complaint quotes itself: "Just as Sid had done to Anne, he left his marriage to Mercedes with another relationship already established."
Bass allegedly bragged to Sperr about "how brilliantly he manipulated Mercedes through their divorce." And the complaint includes another allegation: that Bass told Sperr he had paid Anne's psychiatrist to inform him about Anne's therapy sessions during their divorce proceedings.
Viafora Kress was not the first complication during Bass and Sperr's decade together, according to the complaint. The filing alleges Bass carried on a secret relationship with Patricia Zohn Pfeiffer, a married woman who allegedly stalked Bass and Sperr around Manhattan's Upper East Side. Bass allegedly presented Pfeiffer with agreements designed in part to "secure her silence regarding the affair."
Pfeiffer has not responded to requests for comment.
The complaint paints Viafora Kress not just as a romantic rival but as someone who systematically tightened her grip on Bass's daily life. She allegedly isolated him from longtime friends and employees, exerted control over his communications, household, and spending, and, according to the filing, used his own email account to broadcast their marriage without his involvement. The complaint describes the August 9 ceremony as a "coerced ceremony" and a "sham marriage ceremony."
What evidence supports those characterizations remains unclear. The complaint does not specify, at least in the portions described in public reporting, what makes the ceremony coerced or what proof Sperr offers that Bass did not write the August 22 email himself.
Several other questions remain open. No case number has been made public. The specific legal claims beyond breach of oral agreement and tortious interference are described only as "other claims." And the current legal status of Bass's marriage to Viafora Kress, whether it stands, whether it is contested, is not addressed in the filing as reported.
Oral agreements are notoriously difficult to enforce. Sperr's case will depend on whether she can produce corroboration, witnesses, documents, a pattern of conduct, that supports her claim that Bass made binding promises in exchange for her decade of service. The $400 million figure signals that her legal team believes the evidence is there.
A man's word used to mean something. When it doesn't, courts exist for a reason, and $400 million says Oona Sperr intends to find out whether the law agrees.
