Radiant Core

You are 12 year old Kate Dering,a famous Adventurer who has heard rumors of people Disappearing in a cave.When Kate arrives at the entrance to the cave she hears a moan,and when she goes down the stairs, she finds dead bodies all over the first floor of the cave. When she tries to find an exit, she finds out she's trapped in the floor, due to boulders covering the stairs to the next floor. Kate then hears another moan, and one of the dead bodies gets up, and starts to chase her. She decides to fight it due to being trapped; after the battle, her arm starts to bleed due to fighting a zombie for the first time,she then thinks she is done for.

Then a mysterious man jumps over the boulders and shoots the zombie in the head, killing it and saving Kate from her death. After that the man explains how he heard that a school girl with strange hidden powers was trapped in the cave, and how there are more people getting infected by zombies so he asks Kate to help him. This is the story of Kate's Quest to save the people from Zombies, and to figure out who had done all of this in order to stop it from spreading outside of the cave.