The United States promised Iran will face serious consequences if it’s found to have been involved in an alleged terror plot on U.S. soil. The Justice Department accused an Iranian-American of planning to assassinate Saudi Arabia’s U.S. ambassador with the help of a Mexican drug cartel. The White House said the plot clearly involved senior levels of Iran’s security forces. Iran strongly denied the accusations. Some Iran experts here and abroad voiced skepticism about Iranian government involvement. They say little about the case resembles Tehran’s past actions. An update on the bizarre case and the implications for U.S.-Iran relations.