Can you make Q&A language model stay on topic?

I’m thinking of fine-tuning a pre-trained language model for a Q&A task. More specifically, I’d like to fine-tune the model on a single chapter in a classic college textbook. Afterward, the reader of the chapter should be able to engage in a Q&A session with the model about the content of the chapter. But how do I make sure that the model stays on topic and doesn’t go out of a tangent? I know it is possible when looking at what has achieved, but I don’t know if it will require me to build a model from the ground for each chapter. Can anyone tell me if I’m out of my mind or if it’s feasible?