Cat is just an ordinary American teenager: she goes to an average school, gets fairly good grades and lives a pretty normal life... well, until the Doctor whisks her away in his TARDIS. Even with all of his mad adventures, things end up being more timey-wimey than usual, and she suspects that he knows far more than he's letting on. Now his full-time companion, she has to figure out just what is going on with this Time Lord before... well, before time runs out.