Aunt Polly catches Tom in a lie in the very first chapter of Mark Twain's novel, The Adventures of Tom Sawyer. It was a beautiful day outside, and Polly was curious about Tom's activities of the day. It was right of her to do so, since Tom had played hooky from school. When she asked him if had wanted to go swimming instead of school, he answered "not very much." She was surprised to find Tom's shirt dry, but he suspected what she was up to, so he volunteered that some of the boys had "pumped our heads (with water)." She had even taken the time to sew his collar, knowing that Tom would have to undo it to go swimming. Tom thought he had outfoxed her: He had broken the seam of the collar to go swimming, but he had re-sewn it himself. Aunt Polly was satisfied... until brother Sid spoke up.
"Well, now, if I didn' think you sewed his collar with white thread, but it's black."
"Why, I did sew it with white! Tom!"
But Tom did not wait for the rest. As he went out the door, he said:
"Siddy, I'll lick you for that."
Tom did not want to be the "Model Boy of the village. He knew the model boy very well though--and loathed him." He had forgotten his troubles within minutes.
In this chapter, Tom lies to Aunt Polly when he says he did not go swimming. He is caught in his lie when his cousin Sid points out to Aunt Polly that Tom has the wrong color of thread sewing his shirt shut.
Tom does not feel bad about being caught. What he feels is anger at Sid for telling on him. After he runs away, all he thinks about this particular incident is that he is going to get Sid and that he wishes that Aunt Polly would always sew his shirt with the same color of thread.