Carolyn Hart wrote "Set Sail for Murder" after she took a cruise along the Baltic in preparation for the writing and research for this book. The details of the travel itinerary make for an interesting backdrop to the story. The Riordian family is set on taking a family vacation with their stepmother and her husband. The husband, James A. Lennox, is an old friend and lover of Henrietta O'Dwyer, or Henry O to her friends. Jimmy asks Henry O to go along on the Baltic cruise to help him protect his wife, the famous documentary filmaker, Sophia Montgomery, from her own family. After Sophia has been murdered, Henry O has to prove who was the murderer to protect Jimmy from going to prison.