"Come on, Hermione," Ron muttered desperately.
Hermione had fought her way across to the stand where Snape stood, and was now racing along the row behind him; she didn't even stop to say sorry as she knocked Professor Quirrell headfirst into the row in front. Reaching Snape, she crouched down, pulled out her wand, and whispered a few, well- chosen words. Bright blue flames shot from her wand onto the hem of Snape's robes.
(Harry Potter and the Sorcerer's Stone)
It seems that Hermione had knocked into the front of row behind Snape, and then raced along the row until she reached Snape. If this is right, why is there no perfect tense after the semi-colon?