The man accused of plotting to kidnap talk-show host David Letterman's (search) 16-month-old son and nanny and hold them for $5 million ransom has pleaded not guilty to all charges.

In a court appearance Tuesday, ex-con Kelly Allen Frank (search), 43, denied any involvement in the alleged plot.

Frank appeared briefly in District Court in this small north-central Montana town, on felony charges of solicitation and theft and a misdemeanor charge of obstruction.

Frank spoke only to enter his pleas and to tell Judge Marc Buyske (search) that he was not suffering any medical or psychological conditions. Buyske ordered Frank to remain jailed on bail pending his next court appearance on April 5.

Frank's attorney, Jim Hunt of Helena, declined to discuss the charges against Frank in detail following Tuesday's hearing, but said Frank was "pretty stressed, understandably." He said he intended to ask that Frank's bail, currently set at $650,000, be reduced.

Frank, a self-employed painter, had been hired do to painting work on Letterman's sprawling, 2,700-acre ranch in north-central Montana.

Authorities arrested him last week after an acquaintance told investigators Frank had confided his plot to kidnap Letterman's son, Harry Joseph, and the child's nanny. The acquaintance said Frank talked about holding the two for 48 hours in the belief that he could extort $5 million from Letterman.

According to court records, Frank told the acquaintance he had a key to Letterman's house and even knew where the child slept.

Hunt said his client "has agreed there were discussions about it, but with no purpose of carrying it out."

Hunt characterized the discussion as a "lighthearted conversation."

Frank's fiancee, Laurie Johnson, told the New York Daily News and New York Post that Frank had been falsely accused by a childhood friend he had a falling out with.

She said the estranged friend, who also worked at Letterman's ranch, has a "personal vendetta" against Frank because of a fight they had at work, and has been trying to incriminate him ever since.

Monday night, Letterman started his show with a serious discussion of the alleged scheme to kidnap his son.

"Before we start, I just want to mention a couple of things," the "Late Night" host said.

"Last week, my family and I were involved in a little legal activity, and fortunately everything turned out fine, but I want to just take a second here to thank some people," he said.

Letterman, who was taping his first show since the alleged plot was uncovered, thanked by name two FBI special agents and Teton County's sheriff and county attorney.

He later praised the FBI saying "they know exactly what they're doing," while describing sheriff's investigators as "completely serious and deadly earnest."

He then joked to his bandleader Paul Schaffer (search), "You don't want to cross them. You don't even want to wink at them."

Letterman indicated he couldn't discuss specific details about the case telling his audience, "I have so much to tell you about what happened last week, but I can't."

He did express his gratitude to "the great people of Choteau, Montana," saying that "they have always made me and my family feel entirely welcome as though it were our home, and that's how we think of it, so thanks to those people there."

The talk show host then began to make light of what happened, joking that he wanted to learn about FBI interrogation techniques "because we have staff problems here."

The Associated Press and the New York Post's Rita Delfiner and Ed Robinson contributed to this report.