Ages 9 to 12 years

Now that Dorrie's an apprentice, she has the power to save Petrarch's Library—or destroy it! 

After stumbling upon the secret society of ninja librarians who transcend time and space, Dorrie and her brother have officially become apprentices. They are determined to help the Lybrarians find a missing key that could destroy their beloved fortress, Petrarch's Library. 

On a training mission to 1912 England, Dorrie sees her chance. All she needs to do is get close to a lord with a connection to the Lybrarians' enemy—the Stronghold. But if she arouses his suspicion, she could lead the Strongholders right to the very place she's trying to save…and everyone she cares about.