Isabel features solely in the 1989 television special *Lupin the 3rd: Bye Bye, Lady Liberty*. A high-ranking member of the secret society the Three Masons, she initially serves as Number 2. Beautiful and elegant, she strategically employs her charm to manipulate and exploit men for her objectives.

She is a widowed mother of a son named Michael; her deceased husband remains unnamed. Professionally, she possesses formidable expertise in computer science, having created the powerful Neovirus program. This program can infiltrate and control global computer systems, including nuclear missile launch protocols.

Isabel first appears fleeing Three Masons operatives on an Alaskan train, rescued by Goemon Ishikawa XIII who becomes her bodyguard during her mission to retrieve the giant Super Egg diamond. She manipulates Goemon's romantic interest to ensure his protection. Later, she orchestrates a coup within the Three Masons by seducing Jimmy (Number 3) into assassinating leader Silverman (Number 1), after which she assumes the title of Number 1.

Her motivations blend personal and professional aims. She seeks the Super Egg for the Three Masons and to harness its link to the Neovirus. Her deeper, undisclosed goal involves using the virus to delete global criminal databases, including those tracking Lupin III, fulfilling her son Michael's request to steal the program.

During the ceremony to activate the Super Egg's power, Jimmy betrays her, stabbing her to seize control of the organization and Neovirus. Severely wounded, she is rescued by Lupin III. She reunites with Michael in an elevator alongside Lupin, Jigen, Fujiko Mine, and Goemon. After Michael prevents a nuclear missile launch, Isabel escapes with the group via helicopter. She succumbs to her injuries shortly after sharing a final kiss with her son.