Parallel
Acts 12:9
Nestle 1904 Greek New Testament · Berean Standard Bible
Καὶ ἐξελθὼν ἠκολούθει καὶ οὐκ ᾔδει ὅτι ἀληθές ἐστιν τὸ γινόμενον διὰ τοῦ ἀγγέλου ἐδόκει δὲ ὅραμα βλέπειν
So Peter followed him out, but he was unaware that what the angel was doing was real. He thought he was only seeing a vision.