Свинья и мышь

The story is about a married couple over 40 and without children, who decided that they could not and did not want to live without each other in the literal sense. She is diagnosed with a serious illness, and he says he will follow her. After a very short time, he falls madly in love. Although I couldn't imagine myself next to another woman. What should I do now: Should I say it or not, leave with her, keeping my word? The moral choice the characters face is not easy, but it seems to them that their decision is adult and confident. However, where there is death, love always flashes brightly.