Complex sentence: Surly retrieves it in order to use against putative guard dog Precious, but Andie, who gets the whistle and threatens to dispose of it if Surly does not share the food he is going to take.
Split into simpler sentences: Surly retrieves it in order to use against putative guard dog Precious. Then Surly encounters Andie, who gets the whistle and threatens to dispose of it if Surly does not share the food he's going to take.