Boone's wife, Carla Boone, was sold to Caesar's Legion slavers by Jeannie May Crawford, who betrayed her for a few thousand bottle caps. This led to Carla's disappearance and eventual death. The evidence of this betrayal is found in a Bill of Sale hidden in a safe at the Dino Dee-lite motor inn in Novac. After you gather enough information and confront Jeannie May, Boone kills her in revenge for what she did to his wife