Albert Barnes on Luke 24:18

Art thou only a stranger? &c. This is an expression of surprise that he should be unacquainted with an affair that had made so much noise, and that had been attended with so remarkable circumstances. The word stranger here denotes one who had come to reside at a place only for a time, not a permanent inhabitant. Many Jews came up from all parts of the world to Jerusalem, to keep the Passover there. They appear to have taken Jesus to be such a stranger or foreigner. The meaning of this verse may be thus expressed: "The affair concerning which we are sad has been well known, and has made a great talk and noise, so that all, even the strangers who have come up to remain there but a little time, are well acquainted with it. Art thou the only one of them who has not heard it? Is everybody so well acquainted with it, and thou hast not heard of it? It is a matter of surprise, and we cannot account for it." (k) "Cleopas" Jn 19:25