Accordingly he sent a confidential message to Rome, to ask his father what step he should next take, his power in Gabii, being by God's grace, by this time absolute. Tarquin, I suppose, was not sure of the messager's good faith: in any case, he said not a word to his question, but with a thoughtful air went out into the garden. The man followed him and Tarquin strolling up and down in silence, began knocking off the poppy heads with his stick. The messager at last wearied of putting his question and waiting for the reply, so he returned to Gabii supposing his mission to have failed. He told Sextus what he had said and what he had seen his father do: the king, he declared, whether from anger, or hatred, or natural arrogance, had not uttered a single word. Sextus realised that though his father had not spoken, he had by his action, indirectly expressed his meaning clearly enough; to he proceeded at once to act upon his murderous instructions. All the influential men of Gabii were got rid of (Livy I.54)
Sextus Tarquin might understand the message but do we. Well let us start with the situation. Sextus had arrived in Gabii pretending to be an fugitive from his father- actually he was working as his father's agent. Livy tells us that he had built up his position in Gabii and was slowly becoming their senior military commander not to mention an absolute ruler. Sextus was sending for instructions- and the instructions that he received were in the terms of an image- he was told to cut off the leading men in Gabii so they could not challenge him. As a message to Sextus it works- as a message to Livy's readers, that doesn't tell us much.
Historians have always cast doubt on this story- their main reason is that the same thing happens in a story from Herodotus- a historian writing five hundred years before Livy- who wrote of the tyrant Thrasybulus of Miletus sending a similar message to Periander of Corinth in the same fashion. Herodotus's story is important- because it is obviously the basis for what Livy writes here- and it reflects something very important about Livy and most ancient historian's practice as compared to modern historians. For a modern historian the fact that this story occurs in Livy and occurs in Herodotus makes it likely that one copied the story from the other (directly or indirectly) and suggests that the later story, in Livy, is untrue. For an ancient historian, the simularity suggested exactly the opposite.
We have come across the idea that Tarquin is a tyrant. The point about Herodotus's story is that it illustrated a general principle of how a tyrant governed- a tyrant had to chop the tall heads of his subjects if he were not to be destroyed. For Livy who may well have heard the story from another source (even from the gossip around Rome about Tarquin) the fact that the story was already in Herodotus would have reaffirmed its validity- this is how tyrants behave- rather than calling into question whether the story had been influenced by people reading Herodotus and borrowing from the tyrant of Miletus to describe the tyrant of Rome. Livy assessed his historical characters through a conjecture about the type of character that they were- the type of actions they might perform and made that plausibility his test- this is the type of thing that Tarquin might have done and the fact that other men in the same position had done the same thing in the past, does not call that judgement into question, but reinforces it.
We might deem this invention- it definitely does not meet the standards of historical practice today which is much more cautious about categorising the past in our terms- but in Livy's view it was merely the extension of a type backwards in time. Livy was making a conjecture, depending on the understanding of tyranny he had evolved from his reading, about the way that Tarquin might have behaved and hence presenting to us this story as one that, for him, fitted with the line of Tarquin's character and regime. The other thing that Livy was doing here was making a polemical point about the present day- describing Tarquin as an ideal tyrant and giving Romans a clear illustration about the attitude of the ideal tyrant to his coevals. The point of including the story is that it fits what Livy thinks about Tarquin: it also though provides a graphical illustration of how the Tarquins of the world behave, that Livy wants Romans to take from his history and learn from in the present day.
Reading ancient history, it is often as though the historian collapses time- the modern idea that historical time and attitudes are very different depending upon the period dissolves- and the argument of Livy or Tacitus or Thucydides is that a plausible course of action for a particular type in one era will be so in all others. History is concerned with examining these types. Thus whereas we might well doubt (rightly in my view) that this story has nothing to do with Tarquin and more to do with Romans borrowing from Herodotus: Livy sees the story from Herodotus not as a reason to doubt the tale, but as all the more reason to beleive it. All tyrants are the same and the fact that they do the same thing should not come as a surprise. This is a major and important difference between the way that a modern historian writes history and the way that an ancient historian writes history- and its important to understand when you assess the ancient's veracity, that their idea of historical plausibility may override our stricter notion of historical truth. Ultimately Tarquin for Livy might have done this because he was that type of man- whereas for a modern historian, we need to have a document which tells us that Tarquin did do this.
The two attitudes produce wildly different attitudes to the fact that Herodotus wrote the same story about someone else before hand- for Livy its a sign that tyrants really do behave like this- for us it is an indication to be sceptical- the Roman story could be an echo of Herodotus.