The Legend of Korra - Season 2 Episode 10 -

After successfully arriving in the Spirit World, Korra and Jinora get separated. Jinora ends up at Wan Shi Tong's Library, where she is captured by Unalaq. Korra finds herself in a dark forest as a four-year-old, where she encounters Iroh's spirit. With the help of the former Fire Nation general, she helps a lost dragon bird spirit, who in turn helps her find the spirit portals. There, she is forced by her uncle to open the northern portal, lest he destroy Jinora's soul.