Running frantically through a forest, a young girl named Maebh (Abigail Eames) stumbles upon the TARDIS. Sensing the girl is in trouble, the Doctor lets her in only to discover that she is actually a student of Clara’s. How she found him isn't the only mystery because as he tries to take her back to her teacher, he discovers a forest has erupted not only in the middle of London but all over the world.