。
She came home after dark.
Literal
She [topic-は] dark become [after-てから] home [to-に] returned.
暗くなってから — the い-adjective adverbial 暗く + なる ('become') + ~てから ('after doing'). The whole phrase reads 'after it got dark.' 帰る ('return home / go back') takes に for the destination, but the destination is often omitted when home is implied. ~てから expresses temporal sequence with a slight emphasis — the second action followed only after the first.