In 2015, FRONTLINE took viewers to the secretive stronghold of the Houthi rebels in Yemen, traced the origins of the deadly Ebola epidemic, investigated the hidden history of the CIA’s controversial “enhanced” interrogation methods, revealed the dangers female janitorial workers face while working on the night shift, unraveled new clues to a nearly 30-year-old terrorist attack that brought down a plane in Lockerbie, and continued to document the brutality of ISIS and the Syrian war.

Of the wide variety of investigative journalism we brought you this year, tell us which was your favorite.