Christina Hernon was saved by a doctor at a local hospital when she was 5. Now she’s an emergency physician at one of two Massachusetts hospitals that are due to close on Saturday. She and other staff believe patients like she was could suffer or even die when Nashoba Valley Medical Center and Carney Hospital close because they’ll need to travel to other hospitals farther away. Staff are furious because they say that behind the failure of the company that owns the hospitals, Steward Health Care, lies a story of corporate greed that involves one of their own, former heart surgeon Ralph de la Torre. A Senate committee investigating Steward’s bankruptcy has subpoenaed de la Torre to testify.