On April 26, 2019, a beluga whale appeared near Tufjord, a village in northern Norway, immediately alarming fishermen in the area. Belugas in that part of the world typically inhabit the remote Arctic and are rarely spotted as far south as the Norwegian mainland. Although they occasionally travel solo, they tend to live and move in groups. This particular whale was entirely alone and unusually comfortable around humans, trailing boats and opening his mouth as though expecting to be fed. News of the friendly white whale spread quickly. In early May, a video of the beluga went viral, eventually earning a spot on “The Ellen DeGeneres Show.” By midsummer, he had become an international celebrity, drawing large groups of tourists. All the while, marine experts had been speculating about the whale’s origin. Clearly this animal had spent time in captivity — but where? In the years since the whale, publicly named Hvaldimir, first entered the global spotlight, the very qualities that make...