Agatha Christie's detective novel Murder is Easy has the title with the message that the perpetrator of a serial murder in the English countryside was actually an unimaginable individual, and that murder is easy unless it is imagined. In the novel, arsenic is used as a murder tool. Therefore, and this essay aims to educate the readers about the neurological symptoms of arsenic poisoning. In the future, criminal acts using arsenic may appear before us. For reliable diagnosis, it is a major premise to have the basic knowledge written here; simultaneously, this novel shows that flexible thinking that is not bound by common sense is also required.