An investigation is underway after an 18-year-old high school senior died aboard a Carnival cruise ship. Detectives are reviewing video from the ship and interviewing passengers as the victim's family searches for answers. David Muir reports. https://abcnews.go.com/ | ABC World News Tonight with David Muir

HAPPENING NOW: President Trump signs an executive order on foster care. Follow live updates: https://abcnews.go.com/Politics/live-updates/trump-admin-live-updates-trump-blames-democrats-massive/?id=127478903 | ABC World News Tonight with David Muir

Dazzling waves of color are lighting up the skies coast to coast for the second night in a row in the U.S. Americans from Colorado to Texas are sharing their images of the northern lights display. David Muir reports. https://abcnews.link/doOvozW | ABC World News Tonight with David Muir