In December 1967, Folger met Polish author Jerzy Kosinski at a bookstore party. In early January 1968, Kosinski introduced Folger to his friend, aspiring writer Wojciech Frykowski, at a party and the two liked each other. Frykowski had then been living in the United States for a month.
Frykowski was not then fluent in English, but, like Folger, he was fluent in French. She gave him a tour of New York, began to teach him English, and they fell in love. He moved into her New York City apartment and she supported him financially.
In August 1968, both Folger and Frykowski decided to move to Los Angeles. He wanted to pursue his writing career while Folger wanted to get involved with a new welfare project that was currently under way. She rented a car, and she and Frykowski drove across the country.
In Los Angeles, she found a two-story hilltop home to rent at 2774 Woodstock Road for her and Wojciech in Laurel Canyon, and bought a 1968 yellow Firebird. Their neighbor across the road was singer Cass Elliot of the musical group The Mamas & the Papas, whom the couple quickly befriended. Through Frykowski, Folger met director Roman Polanski and his wife, actress Sharon Tate. Through the Polanskis, Folger and Frykowski were introduced to Jay Sebring. The five quickly began to hang out together and were known to be a part of "the beautiful people crowd" in Hollywood.
On March 23, 1969, Folger and Frykowski were at the Polanskis' home at 10050 Cielo Drive for a going away dinner party for Tate, who was leaving for Rome the next day. Sebring was there, as well as Tate's friend Shahrokh Hatami, an Iranian photographer. Rudi Altobelli, the owner of the Cielo home, had attended the party briefly, but soon returned to his guest house to pack for his upcoming trip to Europe. The incident involved a strange-looking man who had appeared on the property as the occupants of the house sat in the dining room, which faced the front of the residence. Hatami felt uneasy about this stranger roaming the Polanski estate, and went outside to confront the man. From the front porch, the party inside could be seen through the large dining room windows. Hatami asked the stranger if he could help him. The stranger said he was looking for someone by the name of Terry Melcher, a name Hatami did not recognize. Hatami made it clear to the stranger that this was the Polanski residence, and suggested that perhaps the person he was looking for lived in the guest house. During the trial, Hatami identified the stranger as Charles Manson.
On April 1, 1969, while Roman Polanski was away in Europe filming movies, Folger and Frykowski moved into the Polanskis' Cielo Drive home in Benedict Canyon, at Polanski's request.
A day earlier, Folger had quit her job as a volunteer. It was around this time that Folger's relationship with Frykowski began to deteriorate, and she considered leaving him. Constantly fighting, the pair sank lower into the world of drugs which had long passed the experimental stage.
On July 8, 1969, Folger and Frykowski learned that Sharon Tate would be returning to the U.S. later that month. The couple then began to move most of their clothing from Cielo Drive back to their own home on Woodstock Road.
On July 20, 1969, Tate returned to California from London and asked Folger and Frykowski to remain at 10050 Cielo Drive with her until her husband Roman Polanski arrived on August 12. Folger, Frykowski, Tate and Sebring, along with Tate's parents and two younger sisters, all watched the moon landing on television.
On August 6, 1969 film director Michael Sarne invited Folger, Frykowski and Tate over for a dinner party at his rented Malibu beach house. After dessert had been served, Tate began to feel unwell, so it was decided that Folger and Frykowski would drive her home.
On August 8, 1969, Folger and Frykowski ran some errands together.
She and Frykowski then drove back to the Polanski home and had a late lunch with Tate and her friends, Joanna Pettet and Barbara Lewis, on the front lawn patio. The late lunch was served to the party of five by Winifred Chapman, the Polanskis' housekeeper. Shortly after, at around 3:45 p.m., Folger left Cielo Drive in her Firebird in order to keep an appointment she had later that afternoon. Frykowski left minutes later, in Tate's rented 1969 red Camaro, to unload a box at the couple's Woodstock Road home.
That evening, just after 9 p.m., Folger, Frykowski, Jay Sebring, and Tate went out to a Mexican restaurant called El Coyote. Returning home, Frykowski fell asleep on the couch while Folger was in her room reading. Her mother called her at 10 p.m. that night to verify their weekend plans. She was scheduled to fly to San Francisco at 10 a.m. Saturday morning on United Airlines in order to celebrate her birthday.
During the early morning hours of August 9, three of Charles Manson's followers: Susan Atkins, Charles "Tex" Watson, and Patricia Krenwinkel, broke into the Cielo Drive home and killed Folger, Sharon Tate, Jay Sebring and Wojciech Frykowski. Steven Parent, an 18-year old friend of the property's caretaker William Garrettson, was also killed when he encountered the group in the driveway of the home.