On September 27, 2007, the Catholic bishops of Connecticut announced that they would allow the four Catholic hospitals in their state to comply with the state's emergency contraception law. The statement has generated much controversy and criticism from those who are convinced that Plan B is an abortifacient. This essay summarizes and critically reviews the scientific studies that have attempted to uncover the mechanism of action of levonorgestrel, the active drug in the contraceptive commonly known as Plan B. Mounting and recent evidence suggests that this emergency contraceptive has little or no effect on post-fertilization events.