Sarah Golden and Jackie Larsen promised their partners they were out of the detective business. They declared “game over” after both of them almost lost their lives trying to solve their last medical mystery, and they’re happy with that decision: Sarah has finally allowed love and romance into her life, Jackie’s marriage is solid, and Jackie’s son, Wyatt, is still doing great with his year-old kidney transplant.

So when they go on their dream trip to Cuba, they are not looking for trouble. But all their plans go out the window when a desperate plea from a Cuban transplant surgeon puts the duo in serious danger with the Cuban government on the same day the four most prominent immunologists in the world—doctors who were on the verge of solving the huge rejection issues that have plagued the transplant community for more than 50 years—are killed in a car accident in Chicago.

Soon, Sarah and Jackie find themselves dragged into the bowels of investigating venture capitalists and corporate greed—a terrain they know nothing about. As they uncover suspect clinical trials at major US transplant centers, including Sarah’s, their usual friends Biker Bob and Officer Handsome aren’t able to help them much, but they do receive assistance from an unlikely source: Sergio, who they helped to land in prison in Florida (and who is trying to win back his girlfriend), offers his help from the inside. Sarah and Jackie are armed with smarts, humor, and enough persistence to help them face the white-collared demons of corporate America—but with dangerous players gunning for them and death threats being made against their families, will they be able to solve this mystery before someone else gets hurt?