When Erik Torvald, a licensed digger of giant geoduck clams, is found dead of a massive dose of red tide toxin, McKean is called in by police to use his biotechnological genius to unravel the mystery. Did Torvald die simply by eating some of the clams he dug? Or, given the huge quantities of toxin in his bloodstream, was he poisoned? If so, how? And by whom? McKean and his sidekick Fin Morton follow the trail deep into the local Native American culture, encountering resistance both as outsiders and as people who may threaten several native suspects in the case. Among these is Henry George, an old Duwamish tribesman with shamanistic medicine skills and a deep-seated grudge against modern culture. Other clues lead to risky encounters with non-natives who have ties to both drug dealers and the clam fishing industry.
As McKean pursues the case, relying on his labs to study the lethal toxin, he discovers that someone has begun to pursue him. The question soon becomes: can Peyton McKean solve the mystery before he himself becomes the Blood Tide's next victim?