Kate Barlow returned to Green Lake twenty years after Sam's death. It was a ghost town at that point, and the lake was little more than a puddle. The peach trees were gone, but there were oak trees around an abandoned cabin. She lived there, listening to Sam's voice in her head. After three months, Kate woke one morning to a rifle in her face. It belonged to Trout Walker, and he wanted to know where Kate's treasure was.
Remember that Trout Walker's family was the wealthiest in town. The fact that he now feels the need to bully Kate for her treasure suggests that perhaps Trout Walker’s newfound poverty is his punishment, by God or nature, for killing Sam in cold blood.
Kate noticed the woman with Trout as one of her former students, Linda. She'd been a beautiful red headed child, but she looked unkempt and blotchy as an adult. Linda spat she married Trout and they're desperate for money—all of the Walker family's money disappeared with the lake. Linda shouted that Kate must've buried the treasure, and Trout fired the rifle to intimidate Kate. Kate told him to kill her, and said that his grandchildren will still be digging—they'll never find it.
Linda's unkempt appearance suggests that even just associating with the likes of Trout Walker can destroy a person, especially when one also considers her combative nature here. This suggests that both Linda and Trout still believe in their own righteousness and that the town's wealth should be theirs, even though they've done nothing to deserve it.
Linda and Trout pulled Kate out of bed in her pajamas, leaving her boots by the bed. They tied her legs together loosely and made her walk across the hot ground until she showed them where the treasure was. Kate's feet blistered, but whenever she stopped, Linda hit her with the shovel. Suddenly, Linda jumped as a yellow-spotted lizard jumped towards them. It landed on Kate's leg and bit her. She died laughing after telling Trout to start digging.
When Kate dies by yellow-spotted lizard, it recalls the chapter in which the narrator insists that it doesn't matter if one believes in curses or the lizards—this is visible proof that the lizards are deadly, and it also suggests that curses (or the Yelnats family curse, at least) are very real within the world of the novel.