It's 1933, and an older and greyer Hercule Poirot has fallen out of the public eye. When he receives anonymous letters threatening murder, he must take matters into his own hands.
Everyone in the church is killed in the fire. No presuming, it is why the main character feels so strongly about ensuring the dead get justice because of what happened in Belgium. I won't elaborate further because it's a spoiler
A character is dying from what is most likely tuberculosis. She has spells where she gets confused but she later explains that is from the barbiturates she takes for pain. As far as I know there is no cancer.
The second victim Betty is strangled with a pair of stockings. The actual murder is not shown, but later when the police are investigating the crime scene there is a close up of the victim's neck