Silken Threads Tangled Webs

"Silken Threads, Tangled Webs" continues Lucindas story. Previously in "Tarnished Lives, Tainted Dreams," we learned how she and her brothers had grown up in a dysfunctional home. Lucinda had been forced into a relationship with an older man who could have been useful to her father. Following his death, she had given birth to twin boys. Denied further contact with her maternal and paternal relations, she made two lifelong friends, met and married Francis StClair, and gave birth to two more children. The marriage failed, mostly because of Lucindas unrealistic expectations from marriage. Her father had disappeared, shortly after his release from prison, her mother and brothers disowned her, but a mysterious letter had brought her to France, where she made some shocking discoveries about the past.

What was Marcuss terrible secret, and why did Lucindas mother and brothers go to such extreme lengths to make sure she never contacted her Trehearne relations?