FOR MANY YEARS, the so-called “52-hertz whale” has been one of the more mysterious and captivating beasts in creation. So called because the sounds it emits are at a frequency different than all other whales, this particular oddball mammal, which has never been photographed, has captured the imaginations of both scientists and laypeople who assume that it is totally alone, since its fellow whales cannot hear or understand its sonic signature. Whales are complex, intelligent creatures, and in the 52-hertz whale’s much-speculated-upon loneliness, we humans have found a mirror for our own alienation.

In Joshua Zeman’s documentary(executive produced by noted activist stars Leonardo DiCaprio and Adrian Grenier), the filmmaker goes on an expedition to try and find the 52-hertz whale, which hasn’t been heard from in many years. Through interviews with scientists and others, he also surveys the history of whales, their place in the cultural consciousness, and the growing dangers to our oceans. (All of these phenomena are connected, and indeed, the popular 1970 record release Songs of the Humpback Whale played a key role in the burgeoning environmentalism movement.)

The result is a touching, often beautiful film. The Loneliest Whale is certainly informative, but, perhaps more importantly for our day and age, it’s a mood piece that will speak to those who find something evocative and relatable about the story of 52. Does the expedition discover the 52-hertz whale? That would be giving away too much. But the film does end on one rather shocking (and welcome) revelation, one that may lead viewers to reassess our own place in the world.