Why is the company's position particularly perilous at the end of chapter 12 of The Hobbit?
At the end of chapter 12, the company is trapped in Smaug’s cave with the dragon.
Bilbo is able to talk to Smaug and live to tell the tale. He even notices that Smaug’s armor is not flawless, and he has an empty patch on his belly.
As the company is talking, the thrush is listening. When Bilbo tells them about the hole in Smaug’s armor, the thrush hears and leaves to pass the news on.
Bilbo is afraid of the dragon, and tells them to shut the door. Thorin does so, and they realize they are trapped inside with the dragon.
They had hardly gone any distance down the tunnel when a blow smote the side of the Mountain like the crash of battering-rams made of forest oaks and swung by giants. (ch 12)
The company has to wait. They have important information about the dragon and how to defeat it, but they have to get out of the mountain first.
This chapter follows the typical pattern. As soon as they feel safe or achieve some victory, they find themselves to be only out of the frying pan and into the fire. Accomplishing one thing only leads to another problem to solve.