For the remorse of Caracalla put on no shape of repentance. On the contrary, he carried anger and oppression wherever he moved; and protected himself from plots only by living in the very centre of a nomadic camp. Six years had passed away in this manner, when a mere accident led to his assassination. For the sake of security, the office of praetorian prefect had been divided between two commissioners, one for military affairs, the other for civil. The latter of these two officers was Opilius Macrinus. This man has, by some historians, been supposed to have harbored no bad intentions; but, unfortunately, an astrologer had foretold that he was destined to the throne. The prophet was laid in irons at Rome, and letters were dispatched to Caracalla, apprizing him of the case. These letters, as yet unopened, were transferred by the emperor, then occupied in witnessing a race, to Macrinus, who thus became acquainted with the whole grounds of suspicion against himself,--grounds which, to the jealousy of the emperor, he well knew would appear substantial proofs. Upon this he resolved to anticipate the emperor in the work of murder. The head-quarters were then at Edessa; and upon his instigation, a disappointed centurion, named Martialis, animated also by revenge for the death of his brother, undertook to assassinate Caracalla. An opportunity soon offered, on a visit which the prince made to the celebrated temple of the moon at Carrhæ. The attempt was successful: the emperor perished; but Martialis paid the penalty of his crime in the same hour, being shot by a Scythian archer of the body-guard.