Macallan Orsel is a young genetic scientist working in New York City. She discovers that her family is descended from a group of immortals. She also learns that an astonishing secret has been hidden in her DNA, that if activated could bring peace to the civil war that has waged among immortals for centuries. But the same secret also makes her a deadly target by those who are threatened by her potential.

When Macallan was twelve, her parents disappeared during a marine technology expedition in the South Pacific. Afterwards, she came to live with her grandmother, Amelia Orsel, at her lavish apartment in New York across from Central Park. Her grandmother's butler, Satvik, dutifully cared for both Macallan and Amelia for as long as Macallan could remember. For high school, she attended The Spence School in Manhattan before attending Wellesley College for her undergraduate degree in Biology. After briefly working for Merck Pharmaceuticals, Macallan pursued her doctorate at Rockefeller University, where she was awarded the prestigious Letterfeld Grant for her work in primordial genetic mutations. However, Macallan has since broadened the scope of her research and is now focused on unlocking the genetic code that governs the human aging process.

Macallan has also been secretly dating her research partner, James Saltzer.