An obsession is a goal carried to such an extreme that it allows for few other interests in life. Obsessions often destroy the lives of those who have them.
In Holes, obsessions rule the lives of the Warden and Kate Barlow. The Warden is fixed on finding Kate Barlow's treasure and Kate Barlow collected the treasure in her maniac drive to revenge herself on the death of Sam.
The dried-out lake full of holes symbolizes the Warden's obsession. She organizes her whole life around one goal - to find the treasure of Kate Barlow. She creates a reform camp forcing ignorant boys to dig holes, hoping that one of them will find the beloved treasure. She is ruthless, using deception and the force of her will when she can, and physical violence when she must. She has the intelligence to accomplish great things, but her obsession stands in her way. Controlled by her fixation, she leads a joyless life.
Kate Barlow acquired her treasure not because she wanted to be rich, but because she wanted revenge for Sam's death. After the local sheriff threatens to hang her lover unless she gives him a kiss, K.B. kills the sheriff and than gives him a kiss on his dead lips. Her love, Sam, was killed because he was black, his killer is an ancestor of the Warden.
The Warden and Kate Barlow are very different. The Warden is an evil person who uses the legal system for a sinister purpose. Kate Barlow is a good person driven to banditry by the evil done to her. But both end up in their obsessions - they sacrifice their own lives and the lives of others for their fanatical quests.
