HEART OF A LION follows renowned biologist Mark Elbroch deep into the rugged wilds of Wyoming and Washington's Olympic Peninsula, where he has spent years tracking two elusive mothers, F61 and Yoko, as they raise their young on the edge of human territory. With rare, long-term access, this film reveals an intimate world few have ever seen: mothers hunting, protecting and teaching their cubs in landscapes increasingly shaped by people. As Elbroch's connection to the lions deepens, so do the stakes - every movement, every decision, becomes a matter of survival.