Elizabeth Smart's father says teen who vanished with teacher may be brainwashed

The father of Elizabeth Smart says that school teacher Tad Cummins may have 15-year-old Beth Thomas under his spell.

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Ed Smart, whose daughter was snatched from her Utah bedroom in 2002 at age 14 in one of America's most notorious kidnapping cases, told Inside Edition that Cummins is manipulating his former pupil, and is "trying to get her into thinking he's doing her this great favor."

Elizabeth Smart was held captive by Brian David Mitchell and his wife, Wanda Barzee, for nine months. Their brainwashing was so effective that she never attempted to escape. She wore a veil on the streets of Salt Lake City with her captors and even attended parties with them.

"She was threatened that her family might be killed if she didn't comply with what their requests were," Ed Smart said.

He has been closely following Thomas' case. He feels certain that Cummins, 50, is using similar tactics as Mitchell to keep the teen under his control.

"They will try to manipulate in any way possible, to get their compliance or 'be their friend,' be in love with them somehow," he said.

Beth's father, Anthony Thomas, told the Today show Monday that Cummins began to brainwash his daughter after they were caught kissing in his office.

Read: Teacher, Missing Student Spotted in Out-of-State Walmart Days After Disappearing

"Tad had been telling her because of the kissing incident, she would never be able to attend college — never be accepted in college and wouldn't be able to pursue a career after that," he said. "He was owning her mind, convincing her."

He said Beth came to believe that her only option was to run away with her teacher.

Ed Smart told Inside Edition that once Beth is found and returned to her family, the spell will be broken just like it was with his daughter.

"She understood that we unconditionally loved her," he said. "We knew that she had been through hell. Her ordeal was over with."

Watch: Student Claims She Saw Teacher Kiss Girl, 15, Before Alleged Kidnapping