Alternate Character Interpretation: The Course Of Honour: Is Vespasian a well-meaning but clueless idiot who genuinely doesn't realise how much he's hurting Caenis by continually asking things of her that she wants to do but can't due to society's rules, or is he fully aware of what he's doing and trying to get her to realise that they can defy society's rules by just being honest with her?
Fridge Brilliance: In Time to Depart, after the death of Nonnius, Petro is alerted to the death by a team of vigiles who came for him because of the pot shoved on the body's head, their leader just happening to remember that particular pot on the list of stolen property from the Emporium raid. It's a clue that he's one of the many vigiles in Balbinus' employ, who was indirectly sending Petro a message.
Fridge Horror: There's a running subplot in the first few books concerning the possibility that Helena might leave Falco for Titus. She doesn't. However, while it's obviously best for the two of them to stay together, the Flavian dynasty might have lasted a hell of a lot longer if Titus had married Helena and had a few more heirs. They might have kept Domitian off the throne, anyway.
"Funny Aneurysm" Moment: In-text example- in Shadows in Bronze, Falco, Petro and Larius go to Pompeii. One of the first things Falco says about it is that it's obviously a place that intends to last. In the next few lines, he points out that yes, he did know what happened to Pompeii, but it was eight years before the eruption, and everyone who thought Vesuvius was a volcano had concluded that it was extinct. It gets worse when Enemies At Home reveals that Larius died in the eruption, and Falco spent weeks trying to find his body, but to no avail.
In Time To Depart, when Falco first meets Rubella, he speculates that Rubella has a secret sorrow, but laughs it off as a joke. Unfortunately, in Master and God, we find out that Rubella married a woman who bore him a third son- and died two years later. Guess Falco was right.
Genius Bonus: Someone who's read The Twelve Caesars or the Cambridge Latin Course will have a very good idea who killed Sosia Camillina in The Silver Pigs, the moment Falco says what the murder weapon was. For those who haven't, Domitian reportedly liked to tear the wings off flies and stab them with his pen.
Moral Event Horizon: In-story example. As far as Falco is concerned, no matter what he promised Helena previously, Pertinax signed his own death warrant the moment he caused Helena to miscarry their first, unborn child.
Domitian's death in Master and God. It took a long time, mainly because it was a fight between an unfit man who was unarmed, but desperately wanted to live, and an armed man who didn't have many skills and wasn't skilled enough to actually pull off the murder. Vinius had to step in just to finally end it. It was gory.
The death of Rufius Constans in A Dying Light In Corduba. He and a friend tried to do some heavy lifting for a job that should have taken four men at least, not one able-bodied man and another with a sprained back. His chest got crushed by a millstone, and his 'friend' bailed on him and left him to die alone, in agony.
Sosia Camillina's death. She wants to be a Plucky Girl and investigate the conspiracy, and instead she stumbles upon the most secret conspirator and gets stabbed through the heart with his pen.
Tear Jerker: Falco's description of the aftermath of the Boudiccan Revolt, Sosia's death in The Silver Pigs.
The funeral of Geminus and Marcus Didius Justinianus - and the circumstances that led to the baby not getting his own funeral in the first place. Values Dissonance played for heartbreak.
So on the sun-drenched slopes of the Janiculan Hill, one long, strange July evening, we paid our respects to Marcus Didius Favonius. Neither he nor tiny Marcus Didius Justinianus would have to face the dark alone. Wherever they were going, they set off there together, with my tiny son clasped for eternity in the strong arms of his grandfather.
The death of Veronica in The Course Of Honour:
The silence rang out through Veronica's house. Caenis went home.
The fact that even decades after his son's death, Geminus couldn't face writing him out of the will.
Falco and Helena end up having four children. Only two of them make it.
Just after Domitian becomes Emperor in Master and God, there's a chapter that talks about how depressed he now is: he's trapped in the strict customs and regulations of his job, he's now in a position where it is very hard to make close, loyal friends, and most depressingly, he's spent all this effort trying to impress his brother and father, who are both dead. He'll be a good Emperor and run the place well, he'll shower honours over his dead relations and be good to the poor, but ultimately he just wanted affection from two people who are dead.
Gaius and Larius both end up dead. Larius dies in the eruption of Vesuvius, and Gaius dies in the Great Fire.
What an Idiot!: Petro. He's a philanderer, and he decides to fuck Balbina Milvia, a notorious gangster's daughter- to be precise, the daughter of the gangster Petro managed to put away. Of all the women in the world, he went for the one that ensured him a lifetime feud with anyone connected to her.
The Woobie: Petro. He really loves his kids and his wife. His wife leaves him, taking custody of his kids... and then two of them die while he's abroad.
Helena in the first book. She marries young, feeling that she must do her duty to her family, her class and the Empire. She does her best to be the best wife she can be, but her husband is a douchebag who has virtually no empathy for her and doesn't really care. Finally, she divorces him, but that means that she must return to the life of a girl, living in her father's house, under his command. When Falco meets her, she has found an escape, living in a far-off province with very kind relatives, only to have this solitude broken by the reveal of her beloved young cousin's death, and then the arrival of the man who is to take her back to Rome and her father- the same man she thinks slept with her na´ve, sixteen-year-old cousin and possibly broke her heart. (He didn't, but it's hard to judge her for thinking so.)
Albia at the end of Enemies At Home. She contracts dysentery, but suffers from the most severe attack while in a location that nobody knows about. She ends up having to survive several days, naked, in severe pain and surrounded by shit. Thankfully, she gets rescued.