Continuity mistake: Sally and Grover are taking Percy to Camp Halfblood; Sally has her head turned to the right, speaking to Percy. Grover, in the back seat, is looking front as he yells for her to watch out. Sally looks forward, and with a surprised look, swerves left to avoid whatever it is she sees. Then the cow, thrown by the minotaur, comes in from behind, above and to the right and lands in front of the car, a direction in which neither Sally or Grover were looking.