"The Mark of Cain" by Carolyn Wells is a detective novel written in the early 20th century. The story revolves around the mysterious murder of Rowland Trowbridge, a wealthy naturalist. His niece, Avice, is determined to uncover the truth behind her uncle's death, despite the somber backdrop of grief and the conflicting personalities in her household, including her uncle's fiancée, Mrs. Black, and the lawyer, Judge Hoyt. At the start of the novel, we are introduced to Avice’s anxious wait for her uncle, who never returns home at the expected time. Her worry escalates into despair when she learns of Rowland Trowbridge’s violent death in Van Cortlandt Park. The narrative unfolds through a series of telephone conversations and police investigations, establishing key characters including the stern Judge Hoyt and the enigmatic Mrs. Black. As Avice grapples with her uncle's death, determined to find the killer, the tension rises with hints of familial conflict and secrets that may lead to the resolution of the crime. (This is an automatically generated summary.)