Passage 4.20.8
Ἀριστομένης δὲ οὐ πολλαῖς πρότερον ἡμέραις Κεφαλλῆνα ἔμπορον, ἑαυτῷ ξένον καὶ ἐσάγοντα ἐς τὴν Εἶραν ὁπόσων ἐδέοντο, ἑαλωκότα ὑπὸ Λακεδαιμονίων καὶ τοξοτῶν Ἀπτεραίων ὧν ἦρχεν Εὐρύαλος Σπαρτιάτης, τοῦτον τὸν Κεφαλλῆνα ἀφαιρούμενος ἐκεῖνον μὲν καὶ τὰ χρήματα ὁπόσα ἦγεν ἀπέσωσεν, αὐτὸς δὲ ἐτέτρωτο καὶ οὐκ ἐδύνατο ἐπιφοιτᾶν τοῖς φυλάσσουσι καθάπερ εἰώθει. τοῦτο μάλιστα αἴτιον ἐγένετο ἐκλειφθῆναι τὴν ἀκρόπολιν·
A few days earlier Aristomenes had rescued a certain merchant from Cephallenia—his guest-friend and supplier bringing into Eira all the supplies they required—who had been captured by the Lacedaemonians and the Apteraian archers under the Spartan leader Euryalus. While rescuing this Cephallenian and the goods he was bringing, Aristomenes himself was wounded, so severely that he could no longer perform his customary visits to the sentries. This was the most significant reason for the fall of the acropolis.