The Girl in the Castle USED MYS

The world's #1 bestselling author James Patterson delivers a thrilling novel about a teen caught between two worlds and the truths that could set her free—or trap her forever.
 
My name is Hannah Dory and I need you to believe me.  
 
NOW:
Hannah Doe is brought to Belman Psych, kicking and screaming, told she is suffering from hallucinations and delusions.  
 
1347:
Hannah Dory and her village are starving to death in a brutal winter. Hannah seeks out food and salvation in the baron's castle. If she is caught stealing, she will surely hang.  
 
NOW: Hannah knows the truth: she is Hannah Doe and Hannah Dory, and she must return to the past before it's too late to save her sister.
 
Can Jordan, an Abnormal-Psych student, be the one to finally help her? Jordan isn't sure what to believe, and Hannah has even bigger problems: if she doesn't make it back, her sister will die, but if she keeps going back, she might never escape.