Cluster: A potentially fatal disease, a tantalizing romance and international terrorism converge with explosive consequences in

The investigation of a rare blood disease and the development of an unexpected romance come clashing into a sinister international plot. Dr. Dan Murphy is puzzled why his healthy 28 year old brother develops a rare blood disease. As part of an academic course in environmental medicine, he becomes acquainted with Anna Carlson, a young journalist pursuing a graduate degree in public health. With Anna's encouragement, they navigate environmental government agencies, while Anna conducts a research project for her degree to determine the cause of the blood disease, which they learn has affected two other young men. Dr. Murphy is further challenged in his evaluations of unusual symptoms in workers at a local chemical company. Along the way, Dan and Anna fall in love. At the same time, Parker Barrows, a former British intelligence officer who lost his wife and leg in an IRA explosion in London, has nefarious plans to enact revenge and interfere with diplomatic negotiations on the fate of Northern Ireland in the Brexit agreement. As Dan and Anna investigate the cause of the diseases, Barrows and his henchmen continue their plans to sabotage the Brexit negotiations. Dan and Anna eventually determine the cause of the diseases and their paths converge with Barrows' in an explosive ending.