Art expert Emma Kelly arrives at the Metropolitan Museum to meet with disgraced philanthropist Boyle York only to learn he has been murdered. His body and a nearby masterpiece are splattered with blue paint. In the following days, works of art around the world are attacked with the same paint, which Emma believes has something to do with the Virgin Mary. Emma's husband, Elliott Baldwin, the Assistant Director in charge of the FBI's New York City field office, isn't convinced but appreciates her expertise.

Following a lead, Emma travels to her other home in Bath, England, and continues her search for one of the most famous Nazi-looted paintings. When a diver hired to explore a sunken Nazi submarine is murdered with the same weapon used to kill Boyle York, Emma wonders if the art crimes on three different continents are actually an attempt to trip her up.

Emma races against the clock to countries with Virgin Mary apparition sites in an attempt to save the world's most beloved artwork. Can she convince the Vatican to disavow the perpetrators and stop the attacks and bring justice to the mastermind behind them before it's too late?