The 52 Hertz Whale is the cetacean equivalent of a pop-culture phenomenon — a strange creature, known only through recording of whale songs picked up in the Pacific Ocean, who seems to not be a part of any identifiable whale group. Also known as The Loneliest Whale in the World it is a source of pity and fascination among the general public. At PLOS Blogs, Hannah Cheng has a three-part feature on what we do and don't know about the Loneliest Whale. Why, despite 20 years of tracking this thing in sound recordings, do we not have any direct observation of the Loneliest Whale? She's got the answers.