Barbara, thank you very much for your question, and so I looked it up. Throughout the Gospel of John — John refers to himself as “the other disciple,” “that other disciple,” “the disciple whom Jesus loved,” etc., without saying his name, so apparently John also means himself in the Caiaphas’ palace instance:

John 18:15 And Simon Peter followed Jesus, and so did another disciple: that disciple was known unto the high priest, and went in with Jesus into the palace of the high priest.

Something else that I find very interesting is that John wrote the book of Revelation years before he wrote the Gospel of John! Seems like he came down to give it to us because we needed it. I will like to give the source of that; I just wanted to mention it now because it remains surprising and meaningful to me.

Thank you again, Barbara!