Mucius then deliberately placed his right hand in a nearby lamp flame and held it there till it was consumed, to indicate how little effect torture would have on him. Perhaps Portia's self-inflicted wound was inspired by the Mucius legend. And perhaps the tale concerning Portia is no more true than that concerning Mucius.

If the matter of Portia's wound were true, then the fact that Brutus was unaware of a bad wound in his wife's thigh until she showed it to him gives us a surprising view of the nature of their marriage.

Before Brutus can explain the situation to Portia, however, a new conspirator enters and she must leave. Brutus greets him:

—Act II, scene i, line 311

Plutarch calls him Caius Ligarius, but he is named Quintus Ligarius in other places. In either case, he is a senator who supported Pompey and held out for him with Cato the Younger. He was taken prisoner after the Battle of Thapsus, but was pardoned by Caesar after he had been brought to trial, with Cicero as his defender.

Ligarius would have joined the conspiracy sooner but he is sick. As soon as he hears of the details, however, he says:

—Act II, scene i, lines 320-21

This story too is from Plutarch, and it is another example of the kind of heroism Romans loved to find in their historical accounts.

The heavens themselves…

That same night on which Casca has seen supernatural prodigies and Brutus has joined the conspiracy, Caesar himself has had a restless sleep. His wife, Calphurnia, has had nightmares. What's more, she has heard of the sights men have seen and she doesn't want Caesar to leave the house the next day, fearing that all these omens foretell evil to him.

Caesar refuses to believe it, maintaining the omens are to the world generally and not to himself in particular. To which Calphurnia replies:

—Act II, scene ii, lines 30-31

The comets, appearing in the skies at irregular intervals, and, with then-tails, taking on a most unusual shape, were wildly held to presage unusual disasters. For anything else, their appearance is too infrequent. Similarly, the unusual portents of the night must apply to some unusual person.

This makes sense provided astrology in general does.

Caesar does not go so far as to scorn astrology, but he does scorn fear in a pair of famous lines:

—Act II, scene ii, lines 32-33

 Nevertheless, Calphurnia continues to beg and eventually Caesar is sufficiently swayed to grant her her wish and to agree to send Mark Antony in his place.

It is morning by now, however, and Decius comes to escort Caesar to the Capitol. The news that Caesar has changed his mind and will not come staggers him. Quickly, he reinterprets all the omens and hints the senators will laugh. Not only does he make use of the threat of ridicule, but he also says:

—Act II, scene ii, lines 93-96

This seems true enough. Caesar is trying to pull off a coup that runs counter to the deepest Roman prejudices and it was bound to be a near thing. He had failed, at the Lupercalian festival, to gain a crown by popular acclamation. If he now missed a chance to force the Senate to give him one, he would be giving his opponents a chance to mobilize their forces and the whole project might be ruined. The historic Caesar won many successes by striking when the iron was hot and it isn't likely that he would let such a crucial moment pass.

Caesar changes his mind once again and makes the fateful decision to go.

Caesar's progress toward the Capitol is attended by further warnings, according to Plutarch's story, which Shakespeare follows. The soothsayer is there and Caesar tells him ironically that the ides of March are come (presumably implying that all is well). To which the soothsayer answers, portentously:

—Act III, scene i, line 2

Another man, Artemidorus, attempts to give Caesar a warning. According to Plutarch, he was a Greek professor of rhetoric from whom a number of the conspirators had been taking lessons. (In those days, rhetoric, the art of oratory, was indispensable to a public career.) He had picked up knowledge of their plans, presumably because they spoke carelessly before him, and he was anxious to reveal those plans to Caesar (perhaps out of pro-Caesarian conviction or perhaps out of the hope of profiting by Caesar's gratitude).

In any case, he passes a note of warning to Caesar, telling him of the plot. According to Plutarch, Caesar tried several times to read the note but was prevented from doing so by the press of people about him. Shakespeare makes it more dramatic, showing Caesar, by his arrogance, bringing his fate upon himself.

Artemidorus, in an agony of Impatience, cries out, as other petitions are handed Caesar:

—Act III, scene i, lines 6-7

But Caesar answers grandly:

—Act III, scene i, line 8

And thus he condemns himself.

In what follows, Shakespeare follows Plutarch very closely. The conspirators crowd around Caesar on the pretext that they are petitioning for the recall of the banished Publius Cimber, the brother of Metellus Cimber. Caesar refuses, in a fine oratorical display of unyieldingness, saying: