Grip of the Shadow Plague
Third book in the Fablehaven series. Kendra has been asked to join the Knights of the Dawn and as her first quest, she has to go to a secret preserve in Arizona and retrieve one of the five magical artifacts that opens Zzyzx. With the suspicions that the Sphinx could be the leader of the Evening Star and the Knights of the Dawn.
While at Fablehaven, a plague transforms light creatures into dark ones. It is spreading with an incredible speed and anyone knows how to stop it. Will the Soresons and their friends be able to find a way to stop this before it's too late?