Mercy Or Murder is about Roswell Gilbert (Robert Young), an elderly man living in Florida. Having retired, he lives a quiet life and tends to his wife of forty-five years, Emily Gilbert (Frances Reid). Emily is slowly developing Alzheimer's disease, and it is destroying her mind. After watching her condition progress and worsen for over six years, Roswell comes to the conclusion that he must murder his wife to end her pain. He is then arrested and indicted for murder. He claimed to have committed the crime out of love for Emily. What ensues fuels a fierce debate in the USA about euthanasia, which is legal in several countries around the world. Since Alzheimers is not a terminal illness, this defense is dismissed without much of a fight. At his trial, Roswell refuses to apologize for the crime that he had committed. In light of this, the judge sentences him to serve time in prison.