On the next to last night before it all came apart, Stacy Peterson had a tough talk with her sister Cassandra. "We were in her kitchen, and she got close to me and lowered her head, and she asked, 'Do you think I should get a divorce?'" says Cassandra Cales, 22, recalling their evening together on Oct. 26. "I told her I was sort of scared for her. And then as I was leaving, she said, 'If I disappear, look for me.'"

Two days later Stacy did disappear, and now her sister is afraid she will never find her. Illinois State Police launched an intensive search for Stacy, 23, after the petite mother of two vanished Oct. 28, the day her husband, Drew, 53—a veteran police officer in the middle-class Chicago suburb of Bolingbrook, where the couple lived—told investigators he last saw her. But it is a strange incident that happened nearly four years ago that has Stacy's family feeling even more desperate. That's when Drew's previous wife, Kathleen Savio, was found drowned in her bathtub after making allegations similar to the ones Stacy made to her sister—that Drew had threatened and intimidated her. Coroners ruled Savio's death an accident, but in the wake of Stacy's disappearance, investigators are looking at the case again. "I'm just worried about my sister," says Cassandra. "She feared for her life and she wanted a divorce. I just want to find her."

Drew Peterson declined to comment for this article, but he has denied any involvement in Stacy's disappearance and says he thinks she left him for another man. "I believe she's not missing," he told reporters Oct. 31. "She's where she wants to be. I have no reason to suspect foul play." Illinois State Police have interviewed Drew and searched his home, taking a computer hard drive and two rifles. But so far they have not named any suspects. Drew "is being cooperative," says State Trooper Mark Dorencz. "It's a missing person investigation and we're still searching for Stacy."

At the same time, the State Attorney's office is reviewing old files to see if they should reopen the Savio case. In 2002 Savio received a restraining order against Drew after alleging in court papers that "he wants me dead." Relatives say Savio, who was Drew's third wife, decided to leave him when she learned he was seeing Stacy. They argued over splitting up assets, including ownership in a bar, before divorcing in October 2003. In March 2004 Savio was found drowned in an empty bathtub. A coroner's jury quickly ruled out foul play, but, says Will County State's Attorney spokesman Charles Pelkie, "there are a number of unique circumstances that attracted [our] attention." (Drew told reporters Savio "just had an accident ... an unusual accident.")

Drew met Stacy when she was just 16 and working as a part-time hotel clerk; they married in 2003. Those who know Stacy call her an active, devoted mother to her two young children, Lacy, 2, and Anthony, 4—as well as to the two teenage sons from Drew's previous marriage, Tom and Kristopher, who lived with them. Friends recall her helping Tom get ready for his homecoming dance in September. "She put the corsage on Tom, and she was so excited," says her neighbor Brittany Cothron. "She was so proud of him."

But friends and family say Stacy and Drew had not been getting along. "They'd been fighting a lot," says Kaitlyn Holt, 14, who baby-sat for Stacy's kids. "He threatened her and said she shopped too much." Drew told reporters that "there's been mood issues" since Stacy began taking antidepressants after the cancer death of her sister Tina in 2006. Drew also said he last saw his wife the morning of Oct. 28, when she left to help a family friend paint his house. She never arrived, and no one else has reported seeing her that day; police say the last call on her cell phone was made late on Oct. 28.

Hundreds of volunteers have searched the woods around Bolingbrook, to no avail. Neighbors say that Stacy's children are staying with Steven Peterson, 26, Drew's son from an earlier marriage. Her youngest kids, says a neighbor, seem confused: "Last week Anthony said, 'Mom's visiting a friend; she'll be home in a few days.'"

True to her promise, Stacy's sister hasn't stopped looking for her. But through tears she admits she fears the very worst. "She wouldn't just leave her kids," says Cassandra. "I want to find her but she's not alive. I know that. She's never coming back."