Barton heads to Italy to film the period drama Virgin Territory (originally called The Decameron) with Hayden Christensen. They play a nobleman and noblewoman who escape plague-ravaged Florence and tell each other stories to distract themselves from the devastation.
Now 19, Barton begins dating Whitestarr singer Cisco Adler, who is 8 years her senior. The two spend their first Christmas together, snowboarding and skiing in the Colorado Rockies. In May 2006, Adler says that none of the songs on his new album are about Barton because their relationship is going too well. "When you're really happy, you're too busy being happy to write about it," he tells PEOPLE. "I'm happy and Mischa's great."
Stories circulate that Barton is at odds with Hilton, reportedly because Barton wouldn't turn her back on Hilton's then ex-friend Nicole Richie. Perhaps adding insult to injury, Barton broke up with Hilton's pal Brandon Davis and began dating Adler, an ex of Hilton's friend Kimberly Stewart.
Barton's The O.C. character dies in a fatal car crash. Executive producer Josh Schwartz says the purpose of killing off Marissa Cooper was to allow a repositioning of the storyline. Barton heads to Toronto to shoot Closing the Ring and spends the summer studying at London's Royal Academy of Dramatic Art. "I really think it's best to do movies now," Barton, who shoots more than three films back-to-back, tells Newsweek.
Weeks after her 21st birthday, Barton and Adler split. The breakup comes after a nude photo of Adler turned up on a website displaying items from Paris Hilton's storage unit. "Mischa wasn't too excited, to say the least," Adler tells the New York Observer. "I think it was actually worse for her than for me in some ways." Barton's publicist says the pair "parted ways to concentrate on their careers."
Having kept a relatively low profile for the past year, Barton, who will appear in three upcoming films (St. Trinian's, Virgin Territory, and Closing the Ring), poses for the January cover of Maxim. She discusses her bustling transition to film and leaving her The O.C. character behind in a gruesome send-off: "You have no idea how much fun I had doing that [scene]. I was on the set, yelling, "More blood! More blood!"...She needed to go out with a bang."
Barton, 21, is arrested in West Hollywood for DUI and driving without a valid license. After posting $10,000 bail, she is released from jail later that morning. In February, she's charged with DUI and possession of marijuana, and receives three years of probation, a three-month alcohol-education class and a $2,000 fine. Months later, she moves to Paris, France.
After calling police with a health problem, Barton, 23, is placed under psychiatric hold at Cedars-Sinai Medical Center in Los Angeles. "She has been dealing with a lot of personal issues," a pal tells PEOPLE about the actress who has been spotted club hopping in the past few months. "I don't know if she really ever gave up some of the bad habits that had gotten out of control a couple years back."
The former TV star returns to the tube on The CW's The Beautiful Life, an Ashton Kutcher-produced drama about the modeling industry. "I've been fully immersed in production," Barton blogs on her Web site, "and I've been loving every minute of it." The show is cancelled shortly after its debut.
Four years after disappearing from the spotlight, Barton opens up to PEOPLE about the worst of her troubles, when she was admitted to the Cedars-Sinai Medical Center psychiatric ward in 2009 after threatening to kill herself. "It was a full-on breakdown," the actress shares."I was under enormous pressure." Now, Barton is focused on new projects, including her London boutique and the upcoming supernatural film, I Will Follow You, and is happy to be speaking out about her past. "I've learned a lot," she says. "I'm stronger now."
BIOGRAPHY (top to bottom): Flynet; AP; Roger Wong/INF; CW