Antonina therefore received Theodosius as a son consecrated by religion, and in consequence loved him, paid him especial attention, and obtained complete dominion over him.
Afterwards, during this voyage, she became madly enamoured of him, and, being beside herself with passion, cast away all fear of everything human or divine, together with all traces of modesty, and enjoyed him at first in secret, afterwards even in the presence of her servants and handmaidens; for she was by this time so mad with lust, that she disregarded everything that stood in the way of her passion.
Once, when they were at Carthage, Belisarius caught her in the act, but permitted himself to be deceived by his wife.

He found them both together in an underground chamber, and was furiously enraged at the sight; but she showed no sign of fear or a desire to avoid him, and said, "I came to this place with this youth, to hide the most precious part of our plunder, that the Emperor might not come to know of it." This she said by way of an excuse, and he, pretending to be convinced, let it pass, although he saw that the belt which held Theodosius's drawers over his private parts was undone; for he was so overpowered by his love for the creature that he preferred not to believe his own eyes.

However, Antonina's debauchery went on from bad to worse, till it reached a shameful pitch.

All who beheld it were silent, except one slave woman, named Macedonia, who, when Belisarius was at Syracuse after the conquest of Sicily, first made her master swear the most solemn oaths that he never would betray her to her mistress, and then told him the whole story, bringing as her witnesses two boys who attended on Antonina's bed-chamber.
When Belisarius heard this, he told some of his guards to make away with Theodosius, but the latter, being warned in time, fled to Ephesus: for the greater part of Belisarius's followers, influenced by the natural weakness of his character, were at more pains to please his wife than to show their devotion to him; and this was why they disclosed to her the orders they had received concerning Theodosius.
When Constantine saw Belisarius's sorrow at what had befallen him, he sympathized with him, but was so imprudent as to add: "For my own part, I would have killed the woman rather than the youth." This having been reported to Antonina, she conceived a secret hatred for him, until she could make him feel the weight of her resentment; for she was like a scorpion, and knew how to hide her venom.
Not long afterwards, either by enchantments or by caresses, she persuaded her husband that the accusation brought against her was false; whereupon, without any hesitation, he sent for Theodosius, and promised to deliver up to his wife Macedonia and the boys, which he afterwards did.

It is said that she first cut out their tongues, and then ordered them to be hewn in pieces, put into sacks and thrown into the sea.