In France in October 1915, while waiting to welcome President Raymond Poincare, ninety-two-year-old renowned entomologist Jean Henri Fabre reminisces about his past: In 1861, he is a poor assistant professor of science and math in Avignon. Fabre, along with his three daughters, waits impatiently for his wife Marie to give birth. While he paces, his friend, celebrated British economist John Stuart Mill, urges Fabre to publish his studies of insects, particularly his discoveries about the hunting wasp, which paralyzes its victims with a substance that mimics anesthetic. Although Fabre is wary of writing, once he starts that evening, he cannot stop, even to receive the news that his son Jules has been born. His writings on the wasp are not hugely successful, but do impress publisher Charles Delagrave, who continues to print Fabre's work over the next seven years. By 1868, Jules, who also finds insects fascinating, regularly helps his father with his research. Fabre ruminates on the enterprising, hardworking and ruthless insects, which he sees as symbols of larger life lessons for humans. The dean and director of his college, however, do not appreciate Fabre's accessible, popular teaching techniques, and attempt to discipline him. Just before the director can fire Fabre, however, Delagrave arrives with the Minister of Public Instruction, Victor Duruy, who asks to meet the brilliant Fabre. Fabre brings them to his laboratory and details for them the brutality of the female praying mantis. Duruy then asks Fabre to open a coeducational school in Avignon, an appointment that soon scandalizes the town. Soon after, during one of Fabre's outings with Jules, the boy contracts pneumonia. When Mill brings an invitation from Duruy to meet the Emperor, Fabre demurs, afraid he will be censured for his recent, revolutionary findings. Instead, he begins studies of bees and ants, investigating the line between instinct and intelligence in their actions and concluding that all of nature returns to the cardinal law of protecting one's species. Months later, Mill again urges Fabre to go to Paris, and although the scientist is loathe to leave his beloved family, which now includes young son Emile, he agrees. In Paris, Emperor Napoleon III and his court are impressed by Fabre's easy manner and astounding studies. Only Empress Eugenie, who is horrified that Fabre, a commoner, has been awarded the Legion of Honor, protests the suggestion that he tutor their son, the Prince Imperial. Comtesse de la Cour, a beautiful lady of the court, flirts with Fabre and encourages him to stay on in Paris, as does the prince, who adores him immediately. Fabre reluctantly informs the prince, however, that there is another little boy who needs him more, and quickly returns to Avignon. There, Marie, who senses that Fabre was drawn to Paris, breaks down in tears of joy when he kisses her on the cheek and presents her with a lovely lace handkerchief. Soon, Fabre delves into the study of spiders, questioning why humans despise such practical beings. As time passes, Germany takes over France and Napoleon falls, giving the closed-minded local government free reign once again to complain about Fabre's school and writings. When they gather to chastise him for teaching young women the sex lives of plants, Fabre quits in disgust. His landlady, a relative of the governor, evicts him, and it is only the insistent generosity of Mill that saves Fabre's family. Fabre moves to a country home to write full-time, and as the years pass, his desire to provide a secure life for his family mirrors the instincts of the bugs he studies. One day, Fabre is showing the now teenaged Jules how a male scorpion will kill another for a female, only to be eaten by her, when Jules collapses. Within days, the boy has died, devastating his adoring father. Back in the present, Fabre, who remarried and had three more children after Jules's death destroyed his marriage to Marie, struggles to his feet when Delagrave visits. Showing his old friend around his estate, Fabre explains the ingenious inventions which have allowed him to publish the ten volumes that made him famous. Fabre then tells Delagrave that he has learned that man, the only creature to have a spirit as well as a mind, has an obligation not to betray that spirit. As he rises to greet the arriving president, Fabre concludes humbly that he has often failed at this task.