325. When a past tense relating to an event which has not happened is followed by a subordinate clause, the verb of the subordinate clause may also be in a past tense (the event which it expresses being equally imaginary).
Il. 6.345 ὥς μʼ ὄφελʼ ἤματι τῷ ὅτε . . .
οἴχεσθαι προφέρουσα κακὴ ἀνέμοιο θύελλα. . .
ἔνθα με κῦμʼ ἀπόερσε κτλ.
and so 6.350-1 ἀνδρὸς ἔπειτʼ ὥφελλον . . . ὃς ἥδῃ κτλ. and Od. 1.218, also the use with πρίν.
Od. 4.178 οὐδέ κεν ἡμέας ἄλλο διέκρινεν . . .
πρίν γʼ ὅτε δὴ θανάτοιο μέλαν νέφος ἀμφεκάλυψεν
nothing would have parted us
before the dark cloud of death had wrapped us round
This idiom is the same in principle as the use of past tenses in final clauses, which is common in Attic with ἴνα and ὡς.
Soph. O. Τ. 1393 τί μʼ οὐ λαβὼν ἔκτεινας εὐθύς, ὡς ἔδειξα μή ποτε κτλ.
that sο I might never have shown, etc.
When the context has once shown that we are dealing with a purely imaginary event, the indicative serves to carry on the train of suppositions. The indicative is similarly used in an object clause after a verb of fearing, as δείδω μὴ δὴ πάντα θεὰ νημερτέα εἶπεν.