Martha's aunt (Mrs Ivers) was the sister-in-law of Martha's mother, a born Ivers. The sister-in-law married a man named Smith, hence Martha Smith. When Martha's mother died, her aunt had Martha's last name legally changed to Ivers, as she was the sole heir to the Ivers' fortune.
When Sam carries Walter into his room and lays him in a chair instead of killing while he's unconscious, Martha feels betrayed. I thought you loved me,' she says. 'I dreamed of you coming back.' Sam simply tells her that she's sick and that her whole life has been a dream. As Sam tends to Walter, Martha stealthily removes the gun from Walter's desk drawer. When Walter comes to, she points the gun at Sam and tries to get Walter to agree to back up her story that she shot Sam in self-defense, but Walter says nothing. Sam turns his back on Martha and walks out of the room. Martha drops the gun, and Walter pockets it. As Martha watches Sam walk away from the house, Walter embraces his wife and assures her that he won't leave her. He then points the gun at her abdomen. 'You believe me,' Martha says confidently, then puts her thumb through the trigger ring over Walter's thumb and presses it, shooting herself. A voice is heard calling, 'Ivers...Ivers,' but Martha says, 'No...Smith,' and falls to the floor. Sam hears the shot and runs back to look in the window. He sees Walter turn the gun on himself, and another shot rings out. Sam continues to walk away, returning to his hotel room where he finds Toni has returned and is waiting for him. 'I missed a bus once and I was lucky,' she explains. 'I wanted to see if I could be lucky twice.' In the final scene, Sam and Toni are leaving Iverstown. Toni turns to look back, but Sam warns her not to. 'Remember what happened to Lot's wife.' he says. 'Whose wife?' Toni asks. 'Sam's wife,' Sam replies.