Steven Avery, whose story was told in the hit Netflix series "Making A Murderer," is serving a life sentence for the 2005 murder of Wisconsin photographer Teresa Halbach. But that didn't stop him from finding love from behind bars with Lynn Hartman, his new fiancée, who opens up in an exclusive interview with Dr. Phil airing Monday.

WATCH: ‘Making A Murderer’’s Steven Avery's Fiancee Shares About Their Love Story

"Immediately after watching the documentary I felt compelled to reach out to him right away," says Hartman, 53, who wrote Avery a letter. "I told him that I was in the process of a divorce and that I was feeling lonely at home ... I sent a couple of pictures of myself with the letter and asked him if he wanted to write back and forth to get to know each other."

WATCH: Why 'Making A Murderer''s Stephen Avery's Fiancée Said Yes To His Proposal

About two weeks later, she says she got Avery's reply, which she says left her "speechless." Watch the video above as Hartman describes how their relationship escalated, and see what happens when Avery calls Hartman from prison, while she’s on Dr. Phil’s stage, on Tuesday, October 4.