Melissa Hamilton was a young woman who had died and was brought to Carnon Manor.
The rest of the inhabitants of Carnon Manor didn't like Melissa. Nyssa called her horrible and spiteful. Melissa called Nyssa "Miss High-and-Mighty".
When Lord Carnon offered freedom to the house's inhabitants if they would kill the Fifth Doctor, Melissa chose not to take part. She did, however, enjoy the prospect of someone else killing him. (PROSE: The Eternity Contract)