 Sgt. Paul Milner is approached by an old flame, Edith Ashford, to assist in the case of her brother Martin who has been charged with the murder of Tom Jenkins, a sailor who has just been decorated for bravery. The two had apparently had words in the pub and were to meet on the beach soon after to settle their differences. On the face of it, the case seems pretty clear cut but Foyle is puzzled by a number of issues and is not convinced of Martin s guilt. The case takes a strange twist when the sailor s wife, who lives on a nearby farm, contracts a respiratory ailment and dies. Soon after, Samamtha Stewart contracts the same disease and the race is on to determine exactly what is going on in the area. All evidence points to some type of secret biological warfare testing.