she snagged the strap of her pack in one hand and hur-ried on with it banging against her leg , casting mistrustful looks back at the fallen tree and the leafy spaces between the standing ones , afraid of seeing the snake , even more afraid that she might see a whole battalion of them , like snakes in a horror movie , invasion of the killer snakes , star-ring patricia mcfarland , the riveting tale of a little girl lost in the woods and - `` i am not l - `` trisha began , and then , because she was looking back over her shoulder , she tripped on a rock stick-ing out of the mulchy earth , staggered , waved the arm not holding her pack in a doomed effort to keep her balance , and then fell heavily on her side .