A sixteen-year-old girl is missing on the island of Jersey. Aglise is the goddaughter of Lord Royce. After receiving a desperate letter from Aglise’s older sister, Elaine, begging for his help, Royce sends two agents to Jersey to discover what has happened.
Desmond, who loves the excitement of spying, is in charge of the mission. He doesn’t much like his assigned companion, Cadwallon. The two are obviously unwelcome at Warden’s Manor, where Lord Bertrand and his icy wife, Lady Benedicta, manage the island in the name of King Henry I. Bertrand claims the island has been thoroughly searched and no sign of Aglise has been found. Lady Benedicta insists the girl has run off with a lover.
Only Elaine seems genuinely worried about her sister. A quiet young woman, she secretly harbors doubts about the beautiful Aglise’s recent activities. For his part, Desmond is unwillingly drawn to Elaine by her intelligence and her dauntless determination to find her sister.
Meanwhile, in Caen, Normandy, a French spy is plotting against King Henry while he dallies with a noble lady.
Aglise is found buried in a sea cave beneath the cliffs. There’s not a mark on her body, which leads Desmond and Cadwallon to assume she was poisoned. Elaine declares that a necklace Aglise always wore is missing. Later, during the vigil for Aglise in the manor house chapel, Lord Bertrand drops the necklace near the bier.
Upon confronting Lord Bertrand in his private chamber, Elaine, Desmond, and Cadwallon are shocked to learn that he and his young foster daughter were involved in a sexual liaison – an affair that, to the medieval mind, is the same as incest. The fact provides a motive for murder; Lady Benedicta may have killed Aglise out of jealousy.
Cadwallon says he doubts it, because the lady is much too cool emotionally to commit an act of passion. If Lady Benedicta killed Aglise, it must have been for some other reason.
Later, Desmond tenderly comforts Elaine, leaving her yearning for more. When Elaine mentions that Lady Benedicta keeps pigeons, Desmond realizes she may not be raising all of the birds for food. Messenger pigeons have been used for centuries to carry information during wartime, or used by spies.
In Caen, the French spy wonders where his latest message is but, as usual, he distracts himself with sex.
While packing Aglise’s clothing, Elaine discovers a tiny roll of parchment bearing a coded message. When Desmond deciphers the code, it’s clear that Lady Benedicta has been sending information to someone in Normandy. There’s a plot to kill King Henry on May 1. Desmond and Cadwallon have only a few days to save the king, but the island is engulfed in dense fog and no ships can leave.
Can Desmond and Cadwallon reach Normandy in time to save the king? Dare they leave Elaine behind to face the danger Lady Benedicta poses? And what of that intrepid, seductive French spy?
