All cases of poisoning are inherently suspect, and it is by no means incredible that Drusus was not really poisoned, and that the guilty intimacy of Livilla with Sejanus previous to the death of her husband was surmised at a later period when her subsequent conduct had given colour to such a story. According to the narrative supplied to us, Sejanus cannot have been under fifty when this intimacy began, and was probably nearer sixty; Livilla cannot have been less than five and thirty. If the story is true, they were certainly a mature couple of lovers.

It is at least as probable that on the death of Drusus Livilla endeavoured to enlist Sejanus in the cause of her son, and was prepared to marry him, he being only too ready to strengthen his position by such a match, as that Livilla had allowed a violent passion for a sexagenarian to tempt her into infidelity to her husband and actual crime. Again, Sejanus himself is never accused of plotting against Tiberius; had his heart been set upon the throne, he would not have waited for the Emperor’s death, whom in the ordinary course of nature he was not likely to survive long. At the period when the Emperor finally retired to Capreæ, and when he was moving from one villa to another in Campania, the roof of a grotto in which the party were dining suddenly fell in. Sejanus protected the Emperor’s person at the risk of his own life. Had he been impatient for the succession, he would have contrived that a happy accident should open the way to the realization of his ambition.

So far as the records go, we are at liberty to believe that Sejanus made friends with the two probable successors and their supporters in the Imperial family, the elder of whom was Drusus the son of Germanicus; the younger, Tiberius the grandson of the Emperor. By so doing he incurred the enmity of Agrippina and her younger son Nero. He was restrained by no scruples of policy, no ties of kindred, from driving the latter to desperation, and doubtless had many private insults to avenge. He possibly considered it his duty to the Emperor to protect him against the consequences of a pardonable weakness, which Agrippina had hitherto abused, and believed himself to be doing a signal service by eliminating from the Imperial circle such a dangerous conspirator; and he was, unfortunately for himself, so unwise as to use other than straightforward means to secure his ends. Meanwhile, as we have seen, he practically held the regency, he promoted and rewarded at will; he held a court at Rome, and it was generally understood that honours and emoluments were to be obtained exclusively by courting Sejanus. Some of the Senate fell in gladly with the new order, the majority secretly opposed it, and many were bitterly hostile, though restrained from showing their hostility by fear of Tiberius or respect for his long services.

In the year 29 A.D., soon after the death of the aged Livia, a letter came to the Senate from Tiberius charging Agrippina and her son with various offences, and demanding that they should be formally accused and the matter then referred to himself. At this point there is a gap in the Annals of Tacitus. We do not know what the steps were in the process, or what evidence was brought against the guilty. We gather from other sources that Agrippina was banished to the island of Pandateria, and her son to another island, in which he killed himself after a considerable interval, possibly at the suggestion of his guards. Agrippina disappears from history ‘semper atrox,’ for on her way into exile she was so abusive that the centurion in charge of the party was obliged to impose restraint by force, and in the struggle which ensued the lady lost an eye. The historians are silent as to the previous damage suffered by the centurion. Nor did she abandon her contumacious attitude on arriving at Pandateria. It was necessary to feed her by force, and, in spite of the well-intentioned efforts of her attendants, she is said to have succeeded two years later in dying of starvation. Agrippina was not a woman of any real strength of character; had she honestly revered her husband’s memory, and followed his example, she would not have continued the Julian feud and handed it down to two more generations. It is impossible not to feel some respect for so stout and so reckless a hater, and nobody has ever disputed her claim to certain domestic virtues which were lamentably absent from other ladies of her family, and were certainly sufficiently advertised by herself and her admirers; but in her maternal solicitude she was more pushing than wise, and the evil of her example influenced her children more than the good. The mother of Caligula, the grandmother of Nero, was certainly not fortunate in the traditions which she transmitted to her posterity, and if Nero really did poison his half-brother Britannicus, with the connivance of his mother, the cup may be said to have been mixed by his grandmother.

The disgrace of Agrippina and her son Nero brought on the stormy stage of the family politics Antonia the mother of Germanicus. This aged and refined lady had carefully abstained from meddling in the feuds which disturbed the Imperial household. She was now left in charge of the younger children of Germanicus, of the future Emperor Caligula and his sisters. Alarmed by the increasing power of the adverse faction, she began to study the course of public events; she heard that Sejanus was taking advantage of the Emperor’s retirement to tamper with the fidelity of the Prætorians; dark hints reached her ears as to the means by which Agrippina and her son had been entrapped, she feared some yet more terrible catastrophe, and having collected her information, she succeeded in getting it transmitted to Tiberius. The Emperor’s confidence in his trusted friend and servant was shaken; he followed up the evidence, and came to the conclusion that Antonia was right. Suetonius quotes an extract from a private diary of Tiberius, in which he says that he punished Sejanus because he had persecuted the children of Germanicus. There is no reason to doubt the honesty of this statement, though the events which followed have rendered it suspect.

The blow must have been a severe one. Not only had Tiberius been disappointed in a friend, but it was not even certain that he could resume the reins of power and punish the offender if he wished. It is the behaviour of Tiberius at this period which has justifiably gained him credit for proficiency in dissimulation. He did not at once strike; he first of all tested the temper of the Senate by writing coolly on the subject of Sejanus, and sometimes expressing disapproval of his actions, but yet not in such a way as to declare a breach with him. Careful experiments proved that Sejanus had no real hold on the Senate. In the same way means were found of testing the Prætorian guards, and it was satisfactorily ascertained that they obeyed Sejanus simply as the Emperor’s lieutenant. Tiberius took into his confidence Macro, the Commander of the cohorts on guard at Capreæ and in the neighbourhood, and agreed upon a plan of operations with him. Macro went to Rome with letters to the Senate and Sejanus; the attendance of the latter at a meeting of the Senate was particularly requested, it was hinted that unexampled honours were in store for him. When Sejanus went to the Senate House, Macro went to the camp of the Prætorians. The proceedings in the Senate House were purposely protracted. A very long letter was read from Tiberius, the purport of which was for some time uncertain. Gradually it became evident that it was directed against Sejanus, and it concluded with a demand for his arrest. Meanwhile Macro had presented his credentials to the Prætorian guards; Sejanus was superseded, and Macro appointed Prefect in his place; the soldiers proceeded to renew their oath of fidelity to the Emperor, coupled with that of obedience to their new commander. By the time when the ceremony was over, the Senate had risen, and the body of Sejanus was being dragged about the streets.

No sooner had it become apparent that Sejanus was disgraced and no longer enjoyed the favour of the Emperor than the long smouldering hostility to the upstart broke out into a blaze of fury. Tiberius was given no time for repentance or consideration; the fallen favourite was judged and executed on the spot; his two children were similarly condemned and executed; his friends were sought out and assassinated. For some hours, if not for some days, there was a veritable reign of terror at Rome, whose horrors the Emperor in his distant retirement did not at first surmise, and when informed was powerless to check.

This was the end of the careful restoration of the Senate planned by Augustus and fostered by Tiberius, an outbreak of violence which recalled the days of the Gracchi and the proscriptions. Tiberius did not long remain inactive; order was restored, and judicial prosecutions took the place of unlicensed murders. To the Emperor himself the change to law and order brought but little comfort, rather a deeper depth of despair. The whole story of the plots of Livilla and Sejanus, as it was then believed, was revealed. Apicata, the divorced wife of Sejanus, gave possibly tainted evidence of the machinations by which the death of Drusus, the son of Tiberius, had been brought about. Tiberius found that he had been the accomplice of the murderer of his own son, and that in banishing Agrippina and Nero he had played into the hands of that unnatural son and brother the other Drusus. Many of his old and intimate friends were implicated with Sejanus; there had been a conspiracy of silence, if not an active partisanship, and it was difficult to determine the degrees of guilt. In spite of so many years of public service and of single-hearted devotion to the interests of others, Tiberius found that at the age of seventy-two he stood alone in the world, hated and mistrusted by all.

After the first shock, the vigour of the old man returned; he checked the indiscriminate persecution of the friends of Sejanus, and he did his best to secure for them a fair trial. The Empire itself was not shaken by the blow, the effects of which did not extend beyond the city of Rome and Italy; but it must have been a grievous wound to his sensitive nature to discover that his oldest friends did not trust him, and that even such a tried associate as Asinius Gallus followed the example of the many weak-minded men who preferred suicide to facing an inquiry into their conduct. Prosecutions in connection with the Sejanus conspiracy seem to have continued for four years, but the order of events is not quite certain. It is not probable that Tiberius gave orders three years after the event to execute all the prisoners together without further hearing.

As Tiberius himself has generally been credited with responsibility for the disasters which accompanied the fall of Sejanus, it is as well to insist upon the evidence of Dio, who expressly says that Sejanus and his children were condemned by the Senate, and that Tiberius had only demanded his arrest. It had been found necessary on a previous occasion to check the tendency of the Senate to order immediate executions of persons whom they had condemned, and Tiberius had passed a decree that an interval of ten days was always to elapse between condemnation in capital offences and execution, in order that he might be communicated with, and have an opportunity of revising the sentence. The violence with which the adherents of Sejanus were persecuted was really a piece of political vengeance; it was a revival of the old quarrel between the Senatorial and Equestrian parties. In spite of the favour of Tiberius the Senatorial party had not gained upon the Equestrians; in fact, as the business of the Empire increased, the power of the Equestrians had increased with it. Sejanus was only one of many capable administrators whose activity and efficiency was in disagreeable contrast with Senatorial incapacity; the outbreak in which he lost his life was neither concerted nor foreseen. An opportunity occurred for indulging an animosity which had hitherto found its expression in private diaries and drawing-room conspiracies. The way of violence once opened, self-preservation enforced a continuance in that evil path. After the first blow had been struck, root and branch work was inevitable. Sejanus was to leave no avengers behind him.