Answer
Plautianus' treachery referred to the deceit and ambition of Gaius Fulvius Plautianus, the powerful Praetorian Prefect during the reign of Emperor Septimius Severus. Geta, Severus' younger son, perceived Plautianus as a threat to his own succession and warned his father on his deathbed to beware of Plautianus' disloyalty and potential betrayal.