Seventeen year old Arthur Holland is charged with the murder of his twenty six year old step-mother. Mrs. Holland died after consuming poisonous mushrooms which had been offered to her by him. Arthur is an amateur mycologist with a keen interest in collecting mushrooms. The prosecution claim that he was more than aware that they were dangerous and point to his poor relationship with his father after his remarriage. Arthur admits he dislikes his father but says his relationship with his step-mother was good. He argues that he didn't know the mushrooms were dangerous, misled by an inaccurate guidebook.