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.
Textus Receptus (TR) - Acts 12:9 >Καὶ ἐξελθὼν ἠκολούθει αὐτῷ· καὶ οὐκ ᾔδει ὅτι ἀληθές ἐστι τὸ γινόμενον διὰ τοῦ ἀγγέλου, ἐδόκει δὲ ὅραμα βλέπειν.