Sept. 12, 2012 -- The friendly sights and sounds of a neighborhood block party may seem typical, but to one family in White Bear Lake, Minn., it feels nothing short of miraculous.
"This is a great group people in this neighborhood, but it's been a ghost town for two years," said Greg Hoffman in an interview with "20/20."
Greg Hoffman, 56, and his wife, Kim, saw their close-knit, congenial community turn into a ghost town because of Lori Christensen, 49, whom they call "the neighbor from hell."
Watch the full story Friday on "20/20" at 10 p.m. ET
Life in the idyllic Minneapolis suburb had been fine, the Hoffmans said.
"The kids would play with each other. ... Since [Christensen] was a single mom, we would help her out with blowing her snow in the winter, helping her with things like that," Greg Hoffman said.
The Hoffmans said cordial turned to combat five years ago.
"Lori's daughter and us were playing in the yard, painting each other's nails, and she opened the nail polish and just started pouring it in my hair," said the Hoffmans' daughter Keira, 10.
"[Keira] was crying and upset, and she had some fingernail polish in her hair and on her face," said Kim Hoffman. "I didn't think it was that big a deal. I just went over to Lori's, and I said this was what had gone on. I guess immediately she pretty much went off on me. She was yelling and screaming. I turned around and started to walk away."
But the Hoffmans were about to learn that walking away from the wrath of Lori Christensen wouldn't be that simple. And just how vicious her attacks could get became clear when Kim Hoffman, a recovering alcoholic, relapsed and suffered a terrifying overdose of alcohol and pills.
Kim Hoffman collapsed in front of Greg, leaving him and their kids shocked and not knowing if she would live. They called 911 and rushed Kim to the hospital.
The commotion in front of the Hoffman home did not go unnoticed by Christensen, who soon found a way to use the incident against Kim.
"The kids were all playing," said Greg Hoffman, "and Lori came up into the cul-de-sac and started berating the kids, and cussing and swearing."
"I walked up there," said Kim Hoffman, "and I didn't even say anything to her. I said to Keira and Kylie, Come on, girls, let's go. And Lori looked at me, and she basically told me, 'You can't effin' take them. I'm still talking to them.'"
"I took their hands and turned around and kept walking home," Kim Hoffman went on. "And she starts swearing at me: 'You effin' fat whatever, you should have died. Why don't you drink some more scotch?' I never turned around, and I had my two girls' hands, and I just squeezed them and we kept walking in."
This began a string of similar incidents, and the Hoffmans started calling the cops, who became regular visitors to the neighborhood. At first the authorities didn't know whom to believe.
"It took quite a while for Kim and Greg Hoffman to convince me," said White Bear Lake Police Chief Lynne Bankes. "I needed proof beyond a reasonable doubt."
Bankes urged the Hoffmans to gather video evidence of Christensen's harassment, a move that proved to be a game changer in this conflict on the cul-de-sac.
When the Hoffmans' 15-year-old son, Jake, had a birthday party, the camera was rolling for Christensen's latest outburst.
"The kids were out there shooting baskets," Greg Hoffman said, "and Lori took out the remote-control cars and was swerving, [saying], 'I'm too drunk to drive.'"
"She started calling me a 'son of an alcoholic' in front of my friends, and it wasn't something my friends were aware of, so it was an embarrassing situation," Jake Hoffman said.
Family Fights Back at 'Neighbor From Hell' Lori Christensen
The Hoffmans called the police again. Christensen only admitted to "pushing the limit" with her comments.
"It was obvious that Lori wasn't going to stop on our request," Police Chief Bankes said. "There was going to have to be some more serious consequences for her."
In early 2010 the Hoffmans stopped engaging with Christensen. Instead, they went to court and got a harassment restraining order that prohibited Christensen from having any contact with them.
"To not respond to her when she was going after my kids was excruciatingly difficult," said Greg Hoffman.
But the restraining order did little to dissuade Christensen's disturbing behavior. Instead she devised a new and very public way to torment the Hoffmans: 25-foot signs that covered her garage with humiliating messages such as "I Saw Mommy Kissing A Breathalyzer."
"You really wouldn't want to look at them, because the stuff that she would put up on them wouldn't really be appropriate for our eyes," said Kylie Hoffman, 9.
Christensen's continued harassment was a clear violation of the restraining order, landing her in a county workhouse for 30 days as a convicted felon.
"It felt good," Kim Hoffman said. "We actually thought that maybe, you know, it would stop."
"Not even close," Greg Hoffman added.
The Hoffmans say the day after Christensen returned home from the workhouse signs started going up again. If getting locked up didn't stop Christensen, neither did being the subject of local news reports.
"[She was] sitting in my office, across from me," said Bankes. "I said, Lori, why? Why can't you just stop this? What is your purpose? She looked me right in the eye and said, 'It's my lifelong goal to make these people's life miserable.'"
But it was Christensen's life that was looking more and more miserable. On May 19, 2012 Christensen was caught videotaping the Hoffman family as they left their home – another direct violation of the order.
Christensen was arrested and charged with three more felony counts. Judge George Stephenson also sentenced her to an immediate 90 days in jail for violating the probation from her previous conviction. Christensen has since lost her job as an administrative assistant at the Met Council, a regional government agency in Minneapolis.
Most importantly for the Hoffmans, the judge banned Christensen from returning to her home for the remainder of her 4 ½ year probation. The house is now for sale.
Christensen declined requests for comment. Her trial is set to begin Oct. 22 and she has pleaded not guilty.
After five years, more than 80 calls to police, almost 50 citations and enough mugshots to fill a photo album, there was victory for one family unwilling to be harassed by a neighbor. Greg Hoffman said it was worth it.
"People shouldn't have to get up and move because you have a neighbor that is making your life miserable. We took our neighborhood back."
Watch the full story Friday on "20/20" at 10 p.m. ET