Young Dr. Dunn is acting as locum for Dr. Wright, whose practice is on Guernsey, in the Channel Islands. Dr. Dunn finds much of interest in the mix of French and English influences on the island, but nothing unusual about his work, until a strange old man that he has visited goes missing, then turns up dead. Certain peculiarities spark doubts in the doctor's mind about the man's death, while strange circumstances continue to arise and island blackguards threaten from the shadows. Finally, Dr. Dunn reaches out to a friend, Detective Francis McNab, to join him on the island in hopes of examining the accumulating evidence and figuring out just what is going on . . .