What is the plot of Chapter One in The Silver Sword by Ian Serraillier?

In Chapter One, the plot involves Joseph Balicki's escape from prison in the mountains of South Poland.
During the first winter of his incarceration, Joseph is too ill to attempt an escape. In the summer, he feels better and tries to escape with five other prisoners. The attempt fails, however, and Joseph is sent to solitary confinement.
During the second winter, Joseph is ill again. It isn't until the spring that he tries to escape once again. This attempt is successful. When a guard slides Joseph's food through a slot in the door, Joseph is ready for him with his catapult. His catapult is fashioned from sticks and "from the elastic in the sides of his boots." Meanwhile, his "ammunition" consists of a smooth, round stone. Joseph manages to render the guard unconscious with a well-placed shot from his catapult.
Then, with a bent nail tied to a piece of blanket, Joseph manages to retrieve the guard's keys. Once he has the keys, Joseph pulls the guard into his cell and changes into the guard's uniform. Then, he prepares to march out of the prison with the other guards on a routine prison roll call.