Tear Jerker / The Eagle of the Ninth

• Marcus becomes friends or at least friendly with a local tribesman, Cradoc who respects and likes him in return. Then, when the there's an insurrection, Marcus and Cradoc find themselves on opposite sides, with Cradoc being killed by Marcus in battle and Marcus being severely injured leading to his being invalided out of service. Marcus initially feels betrayed but comes to realize that Cradoc did not so much break faith with him as keep a higher faith, as did Marcus as a Roman soldier. From an outside point of view, however, the whole conflict is a tragic waste since the British have a legitimate grievance against the invading Romans, but the local soldiers happen to be decent people who are just maintaining the occupation and have no say in policy.
• In the first chapter, we learn of Marcus' career aspirations and plans to buy back his childhood home when he retires with savings. Then, after just a year of service, he permanently injures his leg which bars him from the army, the only career he knows, and leaves him with no savings, no chance of buying his childhood home and no employment prospects. Pretty rough on someone who's implied to be in his very early twenties.
• Esca's backstory. His tribe rebelled against the Romans and was slaughtered. Esca is now the sole survivor of his family. Luckily he finds a new family with Marcus, Cottia and Cub.
• Guern the Hunter's backstory. He was a soldier in Marcus' father's legion who didn't mutiny but did desert in the route because the psychological exhaustion of being hunted through the woods and picked off one by one by the local tribes proved to be too much. Luckily for him, he also found a new family through marrying the girl who found and cared for him, but if he had any friends or relatives back in Roman territory, he'll never see them again.
• Through the first part of the story, Marcus holds onto the hope that maybe his father's legion didn't mutiny, that there's a more honorable reason they disappeared. Then he learns the truth from Guern, that it was a mutiny, one of the greatest disgraces, and being a soldier, he knows just how much that must have cut his father who led the legion.
• Marcus finally confirms that the tribe he and Esca are staying with are the ones who took the eagle when an older tribesman recounts how they hunted down the survivors of the legion. The tribesman describes how he killed the leader and took an emerald ring from the body as a token which he shows to Marcus who recognizes it as his father's ring.