The Rising Darkness (Prince Caspian fanfic)
It's been nearly two years since Sarah and the Pevensies have returned to their world from Narnia. Ever since, Sarah has once more been plagued with nightmares of the White Witch returning to destroy the peaceful land they had freed from her tyranny. Also during this time, her powers have taken a strange new twist: whenever she gets angry or emotional, they activate.
When all five children are finally called back to Narnia, they learn that not everything is at it seems. Humans have invaded Narnia and forced the inhabitants into hiding. Now they must face not only a human army, but they must also find Aslan. Because for some reason, the majestic lion seems to have abandoned Narnia. They must find him. No matter the cost.