Detectives in Togas (in Germany known as Caius, der Lausbub aus dem alten Rom - Caius the brat from Ancient Rome) is a 1953 children's book by Henry Winterfeld, who was born in Germany but emigrated to America. It's about the Ancient Rome adventures of seven preteen boys (all of them sons of senators) who visit (and constitute) the prestigious school of the old Greek teacher Xanthos.The novel had two sequels: Mystery of the Roman Ransom (1969) and Caius in a Tight spot (1976).
Chekhov's Lecture: At the beginning of the first book, the boys have to learn Greek vocables. Quite boring for them, and probably for the reader too. So it's easy to miss the one that matters later: "ho lukos" - the wolf.
The Comically Serious: It rarely happens that Xanthippus is laughing, about once per book. The first time he does this, the boys can barely believe this.
Conviction by Contradiction: Inverted - at one point Caius claims to have committed the crime Rufus is in prison for (writing "Caius is a fool" on a temple wall). He states that he took Rufus' wax tablet, filled the engraved writing with paint and pressed it on the wall (that's why it looks identical to Rufus' handwriting), but Mucius concludes that if this had happened, the writing would have been in reverse.
Covered in Gunge: Antonius saves his friends from a gladiator in the second book by putting a big bucket of honey over his head.
Disproportionate Retribution: When Rufus writes down the offending words, Xanthos kicks him out from the school - forever. This sets off the plot - Rufus goes to Lukos, thinking he was a real sorceror, to make Xanthos forget to tell Rufus' parents that he's kicked out. Subverted in that Xanthos reveals he never intended to follow through; he was simply trying to scare Rufus.
Dying Clue: After Xanthos reveals where the gold is, it suddenly makes much more sense: "It's behind bars."
Eureka Moment: Caius of all people solves the secret of the letter in book two (see Spy Speak). Take the first two letters of the names, and you'll get Vinicius - Caius' family name. Which means that the bad guys want to kill his father.
Everyone Calls Him Barkeep: The emperor is mentioned several times, but never by name. From the dates given in the story, we can conclude it's Tiberius, second Roman emperor.
Foreshadowing: During the first book, the man at the Baths of Diana tells Mucius that he can't have boys jumping in from the rooftops, because he drains the pool and one will eventually break his neck. Guess what happens to the villain.
Gentle Giant: The baker where the boys like to buy their snacks.
Grammar Nazi: In the German original, Xanthos corrects a student on the use of "anscheinend" (seems to be and could be) and "scheinbar" (seems to be but isn't), nowadays a common cause for complaints. Creates Fridge Logic when you wonder which words they were talking about in Latin.
Hot-Blooded: Caius. Which is the reason he often gets in trouble.
Meaningful Name: Icarus, a wheelcart driver in book 3. He dares too much during a race, and, guess what, falls.
Missing Mom: Caius' is dead, so his sister has to care for the household instead.
No Infantile Amnesia: When they need someone with a good memory, Antonius claims he can remember the time when he was a baby, laid in his cradle and was bored, and could say nothing but "papa" and "mama". Xanthippos states that he can remember his babyhood as well - and the students can barely imagine he ever was a baby.
Noodle Implements: After the boys can't get tickets for the big chariot race, Caius promises he will get them. He doesn't state why he needs a mule and a rope-ladder for this. He stands on the back of the mule and throws the ladder over the wall of the emperor's palace.
Obfuscating Disability: Udo pretends to be a mute, so the bad guys will underestimate him. He only speaks when the boys discuss handing him over to the police - because Rome's police commander is one of the bad guys. - This is also the reason why the boys have enough money to buy him, as a present for Xanthos' birthday.
Oh Wait, This Is My Grocery List: In the first book, the boys write a letter to the emperor to explain that Rufus is innocent. Because they have nothing else to write on, they use the backside of a pergament with Cicero's speech against Catilina on it. When Xanthos wants to read the letter, this trope happens.
The Professor: Teacher Xanthos, who saves the day twice - in the second book, he discovers where the disappeared gold has to be. It's in the false bottom of the cage of a bear. The hint: Said bear in his cage had to be lifted by way more legionnaires than necessary - the hidden gold explained the difference in weight. And in book three, he manages to find out the secret codeword for the Circus Maximus, despite the fact that Caius was thoroughly confused and couldn't remember whether it was the name of "a woman who won a horrible battle" or "a man who almost drowned". It's Pyrrhus (Pyrrha respectively), as in Pyrrhic Victory - Caius had confused the sexes.
Race Against Time: In book three, the last opportunity to convince the emperor to set Caius free will be at the chariot race, because the emperor will leave for Capri where he may stay for months. (As RL Tiberius often did.)
Red Herring: In the second book, the slave Udo tells them he was at a certain place where he heard sounds of swords clashing and someone shouting constantly "Ave imperator, morituri te salutant!" The boys look for one gladiator school and don't find it. And then they stumble upon a blacksmith forging swords with a parrot constantly shouting that phrase and know: Udo was here.
The villain of the first book breaks in at Xanthos' home and steals a few scrolls - and the wax tablet of Rufus, on which he wrote "Caius is a dumbbell". Which he uses to put this sentence in Rufus' handwriting on the temple wall.
Screw the Rules, I Make Them!: In the third book, because of a misunderstanding the secret police thinks that Caius wanted to assassinate the emperor, so he gets condemned to death. Fortunately Ben Gor could save Caius - but the emperor insists he'll have to win the race first.
Slave Liberation: At the end of book two, Xanthos buys Udo's freedom. Although senator Vinicius also offers to do this. It's not stated who exactly buys Udo's freedom at the end, and since he doesn't appear in book three, we'll never know.
Spy Speak: In the first book, the boy Rufus is in prison and about to be executed, but manages to send a strange message to the others: "Rip off the red wolf's sheep's clothing!" He's talking about the "seer" Lukos (Greek for "wolf"), whose name is written in red on his house, who's the Big Bad and framed Rufus. Lukos is really the ex-consul Tellus, who wears a wig when playing Lukos.
Also a letter in book two: "Go to the Viminalis [Hill]. Opposite of the statue of Niobe is the villa where Cicero lived. Usipetes."
And in book three, Claudia sends them a letter which sounds suspicious because she doesn't seem to care for the death of her brother. On the letter are three doodles - two triangles next to each other, a goat's head, and a circle with some lines around it. The triangles stand for a pyramid, the goat for milk - most Romans drank goat milk - and the circle for the sun, or heat in general. Claudia was hinting at an Egyptian technique for hiding messages by writing them in goat's milk, so the letters become invisible, but reappear once you heat the pergament. Antonius helps to come to the conclusion when he states that it's like a riddle of the sphinx.