The day after Tom and Huck’s adventure in the tavern, Becky reminded everyone that she was having a picnic. This interrupted Tom’s thoughts. He stopped dreaming of Injun Joe, and he stopped dreaming of gold. The only thing he could think about was Becky and the picnic.
That night Tom couldn’t sleep. He stayed up, waiting for Huck to call. But Huck didn’t call, so the next morning a sleepy Tom joined the rest of the children at the ferry landing. As they were getting ready to board the ferry, Tom overheard Becky’s mother tell her, "You’ll be getting back late. Why don’t you stay with the Harpers tonight, near the landing."
When Tom heard this, he hatched a plan. "Becky," he said, "let’s spend the night at Widow Douglas’ house instead. She’ll have ice cream."
Becky was about to say no when Tom reminded her that her mother would never know. So she agreed. The ferry dropped the picnickers off at a spot about three miles from town.
After they had eaten and played some games, somebody yelled, "Who’s ready for the cave?" Everyone shouted, "Yay!" So candles were quickly provided, and the children entered the cave.
The cave was a confusing maze of twisting and turning tunnels, but most of the boys knew their way around a lot of it. After a while the boys and girls returned to the cave entrance. Soon the ferry blew its whistle. Night was falling, and it was time to go. The picnickers boarded the boat and amused themselves with tales of their adventures. No one noticed that Tom and Becky were missing.
Meanwhile Huck was watching the tavern. Huck was hiding deep in the shadows when he saw two men leave by the alley door. To Huck’s surprise, one of the men seemed to be carrying a box under his arm. Huck was determined not to let the treasure escape him twice, so he followed the men.
They headed toward the ferry landing, and then a little out of town. They stopped near the Widow Douglas’ house.
"There are lights on," growled Injun Joe. "She must have company."
"Maybe we shouldn’t do this," said the second man.
"No way," said Injun Joe. "I want revenge. Her husband horsewhipped me, but he died before I could—"
"Are you going to kill her?" interrupted the other man. "I won’t do any killing."
"Kill? Who said kill?" answered Injun Joe.
Huck had heard enough. He turned and slowly moved away. Once he was sure that he couldn’t be heard or seen, he ran.
Huck stopped at the first house he came to. It was the Welshman’s house, and he banged on the door. As soon as the Welshman opened the door, Huck told him that Widow Douglas might be in danger. The Welshman and his sons grabbed their guns and ran into the night. Huck returned at dawn to learn what had happened.
"Sit down, boy," said the Welshman. "First we’ll have breakfast, and then we’ll trade stories."
After breakfast Huck learned that Injun Joe and his partner had gotten away, but that the box contained only thieves’ tools. Huck told the Welshman almost everything he knew. The Welshman was shocked that he and his boys had almost captured Injun Joe.
All through the morning Huck stayed out of sight because he didn’t want anyone to know that he was involved. The Welshman had a lot of visitors who wanted to hear the tale, and he told them. But he never mentioned Huck’s name; instead he described a mystery man who had warned him of the crime.
Soon the town was as curious about the mystery man as they were about the crime. But the Welshman wouldn’t reveal Huck's identity. Although there was no Sunday school during summer vacation, the whole town gathered at the church. People wanted to hear more news about the thieves and the mystery man.
Before long a new mystery appeared: where were Becky Thatcher and Tom Sawyer? No one knew. Judge Thatcher organized a search party, and the group went to the cave. They looked for Becky and Tom for three straight days, but were unable to find them. The only thing they found was Tom and Becky’s names written on the wall of the cave.
While Huck was following the thieves and most of the town was sleeping, Tom and Becky had become lost in the cave. Tom was an experienced explorer, but while he was with Becky, he had forgotten to mark their path. When he realized they were lost, it was too late. Becky cried, and Tom did his best to comfort her.