Final answer:
The boy is troubled by his father's arrest due to feeling abandoned but finds comfort in studying astronomy and planning for a future where he can demonstrate his capabilities.
Step-by-step explanation:
The most troubling detail of the father's arrest for the boy is the sense of abandonment and the lack of familial support, as he could not see his mother and his father was too afraid to come near him.
Yet, the boy finds solace in education and the world of astronomy, as his father provided him with books. This knowledge empowers him to aim for a future where he can make his true power felt in a place far from the troubles of his current life.