After the Lake Incident, Lily Evans is not looking forward to school. She has to figure out her relationship with the Mauraders, her ex-friendship with Severus, and NOW someone is attacking the muggleborn students. If Lily wants to survive another year, she's going to have to ask for help.

Something happened in the graveyard that night. A spell no one predicted and an event set-off. Priori Incantatem turns out to be more than just seeing ghosts but a reversal of the spells all together. And those spells are decades old. (Harry time travels to the first war).