When Lydia was arrested for the murder of Charles, Marta’s prints were discovered on the bottle of cat poison, naturally. She never denied that, saying that she sold Lydia the bottle. When Philip declared that if the murderer was not found in a certain amount of time that Diana and Lydia would both be convicted of the murder, Marta visited Lydia and Diana saying that she was sorry and if there was anything else she could do, she would do it. This led to the two working up a scheme to scapegoat Marta by creating a holo-vid that showed Marta in love with Charles and saying that if she couldn’t have him, no one could. Marta was convicted of Charles' murder, and - as per the traditional Visitor legal code - she was forced to lie awake next to Charles' corpse as they shipped out into space.