Dr. Grogan is an Irish doctor who lives in Lyme. He and Charles find common ground in their intellectual pursuits, particularly their dedication to Darwin’s theory of evolution. Grogan believes that Sarah is not only melancholic, but also psychologically twisted. According to him, she is making herself miserable on purpose in order to manipulate the people around her, particularly Charles. Grogan wants to put Sarah in an asylum, and despite Charles’s great respect for Dr. Grogan, he struggles to believe that Sarah is wicked or crazy. Later, Grogan harshly reprimands Charles for choosing Sarah over Ernestina, telling Charles that he must live the rest of his life in a way that will prove he’s made his choice with the right motives. Overall, Grogan acts as a moral counterweight to Charles; his arguments differ from Charles’s, but make just as much sense—perhaps more.