Immortal Red is the story of Turritopsis dohrnii, a dime-sized jellyfish with a bright red stomach and the gift of immortality. A marine biologist snorkeling off the coast of Cape Fear, North Carolina makes a chance discovery of this unusual creature. At the moment of death, due to old age or massive trauma, Turritopsis has the ability to fully rejuvenate and emerge as a young adult. After observing numerous repetitions of this phenomenon in her lab, the scientist nicknames the little invertebrate Immortal Red.

A search for funding leads her to the octogenarian head of a shadowy black-ops division of the CIA. A scientific breakthrough, discovery of ulterior motives, and a subsequent attempt to hide success put the scientist and her CIA husband on the black-ops hit list. Fearing the worst, she transfers cryptic clues to the research to her daughter Chloe with disastrous results.

Chloe, a graduate student, is now a designated terrorist on the run with her mother's research journal, a large squarish key to God-knows-what, and a 22-year-old Airedale Terrier with more lives than a cat.

She finds aegis in the person of Thomas Whitefeather, a retired marine veteran who owns a café in a small North Carolina town. Thomas, a Cape Fear Indian, the last survivor of a tribe that disappeared two centuries ago, is all too familiar with the jellyfish.

Nick Caedwallen, PhD in ancient history and archaeology, took a wrong turn somewhere and became the go-to guy for what the CIA jokingly refers to as the PDD or Plausible Deniability Department, resolving problems that the rest of the clandestine services find "too hot to handle."

Nick has been dispatched to recover the research data and deal with the Spencer girl. A revelation regarding his own mortality and the realization that he has strong feelings for his target places him on a collision course with his old boss and the full resources of the black-ops organization.