The fiancee of a Montana man charged with plotting to kidnap David Letterman's son said her husband-to-be is being falsely accused by a childhood friend he had a falling out with.

Kelly A. Frank (search) was arrested Monday after the estranged friend told authorities that Frank had confided a plan to kidnap 16-month-old Harry Joseph Letterman (search) and his nanny for $5 million in ransom.

Frank, 43, and the informant not only had been friends since they were 10 but also had worked together at the talk-show host's ranch, west of Choteau, Mont., said the fiancee, Laurie Johnson.

In interviews published Saturday, Johnson told the New York Daily News (search) and New York Post (search) that the estranged friend has a "personal vendetta" against Frank because of a fight they had at work, and has been trying to incriminate him ever since.

Johnson said the informant twisted an offhand remark Frank had made about Letterman increasing security at the ranch into a threat against the child.

"He has always had great respect for Letterman," Johnson, 40, told the Daily News. "He felt privileged to be able to go up there and work for him."

Frank is charged with felony solicitation, felony theft for allegedly overcharging Letterman for painting work and misdemeanor obstruction for allegedly lying to an FBI agent who first questioned him about the plot.

He is being held on $600,000 bail and is scheduled to make his next court appearance Tuesday. Authorities in Teton County, Mont., said it was not clear whether Frank had an attorney yet. He had not been assigned a public defender as of Friday afternoon.

Frank previously pleaded guilty to stalking and intimidating a woman who alleges he also kidnapped and raped her.

He is on probation in the stalking case, with a 10-year suspended prison sentence, but Lewis and Clark County petitioned a judge Thursday to revoke his probation after learning of the alleged plot targeting the talk-show host's only child.

The woman Frank admitted stalking obtained protective orders against him, but he was charged at least twice with violating them, according to court records. Court documents were not clear about the relationship. Frank has been divorced more than once.

The woman told Helena, Mont., police that beginning in the spring of 1997, Frank stalked and harassed her for months. She said that one occasion he raped her, and in another, he kidnapped and drove her from Helena to Seeley Lake, more than 100 miles away.

Frank received a six-month county jail sentence for stalking and a suspended, 10-year prison sentence for intimidation.