A cable TV network will feature an Oklahoma murder case Thursday at 8 p.m. Central time. Investigation Discovery network will air an episode on the unsolved murder of rancher E.C. Mullendore.

The millionaire rancher was beaten and shot to death on his ranch in Osage County in 1970. At the time, Mullendore had the most expensive life insurance policy in the nation, $17 million, which led to endless speculation and rumors.

The cold case will be featured on a series called "Behind Mansion Walls." It includes interviews with private detective Gary Glanz and Andy Surritte, a friend of the victim.

The chief suspect in the Mullendore's murder, ranch hand Chub Anderson, died in 2010. He took any first-hand knowledge of the crime to his grave.

Investigation Discovery airs in Tulsa and Oklahoma City areas on the following channels:

Cox Channel: 103/HD 761
AT&T U-verse: Channel 260/HD 1260
DirectTV: Channel 285
DISH Network: Channel 192