Janai Norman reports from North Plainfield, New Jersey, where two people died after flash floods struck the region on Monday night during rush hour as torrential rain inundated the Northeast, and Ginger Zee tracks the potential tropical system that's expected to bring heavy rain from Florida to Louisiana through end of the week; Trevor Ault has the latest on the investigation into the "American Idol" producer and her husband who were found shot to death in their Los Angeles home; Matt Gutman has details on the murder trial of the former Colorado dentist accused of killing his wife of 23 years with protein shakes laced with cyanide, arsenic and a chemical commonly found in eye drops; and more on tonight's broadcast of World News Tonight with David Muir.