Bonanza - Season 4 Episode 16 Song in the Dark

Adam's guitar-strumming friend, ranch hand Danny Morgan, is arrested on suspicion of murdering and robbing the Widow Baker. Someone had reported hearing Danny singing outside her place at the time of the murder. More, importantly, Morgan has bad scratches on his arm, and the widow was found with human skin under her fingernails. Adam is thoroughly convinced that Danny couldn't have done it; the two became friends after Danny saved Adam's life a few years ago.