Passage 1.10.3
εἰώθασι δὲ ἀνθρώποις φύεσθαι διʼ ἔρωτα πολλαὶ συμφοραί. Λυσίμαχος γὰρ ἡλικίᾳ τε ἤδη προήκων καὶ ἐς τοὺς παῖδας αὐτός τε νομιζόμενος εὐδαίμων καὶ Ἀγαθοκλεῖ παίδων ὄντων ἐκ Λυσάνδρας Ἀρσινόην ἔγημεν ἀδελφὴν Λυσάνδρας. ταύτην τὴν Ἀρσινόην φοβουμένην ἐπὶ τοῖς παισί, μὴ Λυσιμάχου τελευτήσαντος ἐπʼ Ἀγαθοκλεῖ γένωνται, τούτων ἕνεκα Ἀγαθοκλεῖ ἐπιβουλεῦσαι λέγεται. ἤδη δὲ ἔγραψαν καὶ ὡς Ἀγαθοκλέους ἀφίκοιτο ἐς ἔρωτα ἡ Ἀρσινόη, ἀποτυγχάνουσα δὲ †ἐπὶ τῷ βουλεῦσαι λέγουσιν Ἀγαθοκλεῖ θάνατον. λέγουσι δὲ καὶ ὡς Λυσίμαχος αἴσθοιτο ὕστερον τὰ τολμηθέντα ὑπὸ τῆς γυναικός, εἶναι δὲ οὐδὲν ἔτι οἱ πλέον ἠρημωμένῳ φίλων ἐς τὸ ἔσχατον.
Through love, it is customary that many misfortunes befall mortals. For Lysimachus, being already advanced in age and esteemed fortunate in respect to his children—Agathocles among them, born of Lysandra—married Arsinoë, Lysandra’s sister. This Arsinoë, fearing for her own children, lest after Lysimachus' death the power should pass into the hands of Agathocles, is said, for these reasons, to have plotted against Agathocles. Others recorded that Arsinoë conceived a passion for Agathocles, and after being rejected by him, devised death against him. It is also told that Lysimachus later became aware of the daring deed done by his wife, but he was already so utterly bereft of friends that no advantage remained for him thereafter.