Hamilton is a Scottish alchemist residing in Japan after marrying a Japanese woman. His most significant documented action involves unethical experimentation on his daughter, Lili Hamilton, granting her psychic abilities like mind reading and emotional understanding. These experiments require Lili to take regular medication to manage side effects and maintain stability. Hamilton's primary motivation is pursuing the Philosopher's Stone, which he believes is embedded within the gargoyle statue Gar-kun, created by fellow alchemist Iyo Takahara.

He employs manipulative strategies to obtain the Stone, directing Lili to feign illness and befriend the Yoshinaga family to access Gar-kun. Hamilton collaborates with the phantom thief Hyakushiki, deceiving him into capturing Gar-kun under the pretense that the Stone could cure Lili. During the riverbank confrontation, Hamilton betrays Hyakushiki, shooting him and revealing his true intentions solely focused on acquiring the Stone, not helping his daughter. He deploys his own alchemical creation, the headless robot Dullahan, to secure Gar-kun during this event.

Hamilton demonstrates consistent antagonism without redemption, showing no remorse for exploiting Lili or endangering others. His actions directly lead to Dullahan's defection, as the robot later abandons him to protect Lili. Hamilton maintains associations with other antagonistic figures like Amane Higashimiya, though their partnership fractures when Higashimiya disapproves of his methods. Hamilton persists as an active threat seeking the Philosopher's Stone, with no narrative indication of reform. His background as a widower and relocation to Japan establishes context but does not mitigate his unethical pursuits.