Prosecutors reached a plea agreement with the man accused of plotting to abduct David Letterman's (search) young son, allowing him to plead guilty Monday to lesser charges and dropping a kidnapping-related charge.

Kelly Frank (search) pleaded guilty in state District Court to felony theft, misdemeanor obstruction and possessing illegally killed wildlife, a felony. In exchange, Teton County Attorney Joe Coble dropped a felony charge of solicitation, which accused Frank of plotting to kidnap the talk show host's son from the Letterman ranch.

The agreement calls for a 10-year sentence on the theft charge and lesser terms on the other pleas.

Frank, who had worked on the ranch near Choteau in north-central Montana, was arrested in March after an acquaintance told authorities that Frank had talked of a plan to kidnap Letterman's then 16-month-old son, Harry Joseph, and the boy's nanny.

The acquaintance told authorities that Frank intended to hold the two for 48 hours on the belief he could extort $5 million ransom from Letterman. Frank previously pleaded guilty to stalking and intimidating a woman who alleges he also kidnapped and raped her.

Coble said he agreed to dismiss the solicitation charge because he believed the plea agreement accomplished what he wanted.

"Kelly Frank needed to go to prison. This gets that done," he said after Monday's court hearing.

Frank's attorney, Jim Hunt of Helena, said his client agreed to the plea deal because he understood "that there was a risk in going to trial."

"He feels badly for the anxiety that this has caused the victims in this case and he wishes it hadn't happened," said Hunt, who insisted Frank's remarks about a kidnapping were merely "light-hearted conversation" and not a serious plan.

In addition to the 10-year sentence on the theft charge, which accused Frank of overcharging Letterman for painting, the agreement calls for a six-month sentence on the obstruction charge and five years on the wildlife possession charge. The latter two sentences would be served concurrent to the 10-year term.

The obstruction charge accused Frank of lying to investigators who originally questioned him about the plot. The wildlife possession charged was filed only Friday as part of the plea agreement; it accused Frank of having large mule deer buck that had been poached in January or February.

District Judge Marc Buyske said he would decide whether to accept the plea agreement after reviewing a pre-sentence investigation. Sentencing was tentatively scheduled for Sept. 13.

Tom Keaney, spokesman for Letterman's production company, did not immediately return a call seeking comment Monday.

Harry was born Nov. 3, 2003, to Letterman and his girlfriend, Regina Lasko (search), and named for the comedian's late father.

For years, Letterman was targeted by a stalker, Margaret Ray, who called herself "Mrs. David Letterman" and broke into his Connecticut house at least seven times. She eventually pleaded guilty to breaking and entering. Diagnosed with schizophrenia, she served 10 months in prison and 14 months in a mental institution. In 1998, she committed suicide at age 46.