Task: Question Answering
Input (English): Passage: Tessibel Skinner is a young woman in a squatter village on the coast, where she lives with her father, a local fisherman. Towering above the village is the estate of Elias Graves, a wealthy man who hopes to use his influence to remove these squatters from his land. When his lawyer is unable to so directly, he instead enacts a ban on net fishing, removing the livelihoods of many people in the village, including Tess and her father.
Despite the ban, some continue to fish illegally, though they are soon confronted by men sent by Graves. In this confrontation, one of Graves' men is shot and killed. Tess' father is wrongfully accused of the murder and arrested. Meanwhile, through these altercations Tess meets Frederick Graves, Elias' son, who is home on a break from his theological studies. Before long, the two begin a forbidden romance. Also on break with Frederick is Dan Jordan, a friend from his fraternity, who simultaneously falls in love with Frederick's sister, Teola.
Soon after Dan and Frederick return to college, Teola learns that she is pregnant and struggles to decide if she should tell Dan. Her decision is made for her soon enough, as she receives a letter informing her that Dan has died heroically in a fire at the fraternity. Unable to confide in her very stern father, Teola is distraught and turns to Tess for support. Once the baby is born, Tess agrees to take the child and bear the social stigma of having a child out of wedlock.
Upon his return, Frederick is forced to shun Tess for her sin despite his remaining love for her. Soon, however, Teola's baby falls ill and Tess decides to take him up to Elias' church to be baptized. Disgusted by Tess and the child, Elias refuses, shaming them publicly. Teola, having witnessed her father's anger, decides to step forward and admit the truth about her child. Tess is forgiven and it is decided that Teola will die with her son. Meanwhile, the true murderer is found, allowing Tess' father to be released from prison. 
Question: Whose sister's baby does Tess pretend is hers?
Output (English): Frederick's.