Out of the Past

After Tarrlok has taken Korra hostage, he fabricates a story, telling everyone that the Equalists took her. When Tenzin and former Police Chief Lin Beifong hear this, they set out to find her, with Lin recruiting the help of Asami, Bolin and Mako.
While being captured, Korra takes the time to understand the visions that she's been seeing. What is the message that Aang is trying to pass onto her? And will Tenzin and the others find out what really happened to Korra and be able to find her?