LOS ANGELES - Robert Stack, whose granite-eyed stare and menacing baritone spelled trouble for television's fictional criminals in "The Untouchables" and real ones in "Unsolved Mysteries," died at his home. He was 84. Stack's wife Rosemarie found him slumped over at about 5 p.m. Wednesday. He died of heart failure, she said. The actor had undergone radiation treatment for prostate cancer (news - web sites) in October. "He was feeling so good," she said Thursday. "He had a bout with a tumor but that was gone. It wasn't that, it was his heart. He was too weak. He wouldn't have...