Plot summary
In the spirit world with Jinora, Korra must contend with the difficult relationships between spirits. When the two are separated, Korra is transformed into a childlike version of herself. She is rescued by Iroh, who has "retired" into the spirit world and who teaches her that she must exert strong control over her emotions in the spirit world, among other lessons, allowing Korra to travel to the Tree of Time, where the portals meet in the spirit world. Meanwhile, Jinora finds Wan Shi Tong's library and convinces the Spirit of Knowledge to allow her to learn about the spirit portals.
While learning that Vaatu's seal can indeed be broken if both portals are opened during Harmonic Convergence, Jinora learns that Wan Shi Tong is in league with Unalaq. Attempting to rescue Jinora, Korra is forced by Unalaq to open the northern portal. After a short battle, Korra is rescued by a friendly spirit and forced out of the spirit world without Jinora, whose inanimate physical body remains in a coma-like state.
Credits
Adapted from Wikipedia contributors, The Legend of Korra season 2. HTML formatting and reference markers removed.