Missing Mom's Father-in-Law Says She Ran Away

Susan Powell's father-in-law is speaking out nearly one year after the wife and mother went missing, saying he thinks she ran off with another man. INSIDE EDITION talks to Susan's parents about the case.

The husband of a woman missing for nearly a year is speaking out for the first time, and what he's saying may shock you.

Josh Powell tells the Salt Lake City Tribune his missing wife, Susan, is "extremely unstable." And his father told the newspaper she ran off with another man, saying, "Susan is very sexually motivated."

28-year-old Susan Powell disappeared from her home in Utah last December.

Her husband became a person of interest after claiming he took his two boys on a midnight camping trip in a blizzard the night she disappeared. He now says he believes Susan is still alive, but afraid to come home because she fears the public will turn on her.

"She knows she will be chewed up like hamburger meat when she comes home," he said.

Now, Susan Powell's parents are hitting back, claiming it's Josh's family that has a history of mental illness, including bipolar disorder and schizophrenia.

"She's one of the most stable persons that there's ever been," said Susan's father, Chuck Cox.

INSIDE EDITION's Megan Alexander said to Chuck and Judy Cox, "He says that Susan ran off with another man. How do you responde to that?"

Susan's mother, Judy Cox, said, "That's false because her idea, or her goal, was to always be married and have a happy family. And that includes the husband, and her marriage was important. She kept trying to make it better."

Chuck Cox said, "We would have known if there was a possibily if there was another man or something. Or one of her friends would have known. Somebody would have known something about this."

They say they have been stopped from seeing their grandchildren, who live just four miles away in Washington state.

"We certainly wouldn't have said anything negative about their father or their family or anything. We just want to see the two grandchildren," said Chuck Cox.

Their last poignant link with their mising daughter is listening to her saved voicemail messages in which Susan said, "Where are you? Hope you're having a good day. Say I love you grandma."