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 court of the high priest.
All Commentaries on John 18:15 Go To John 18
George Leo Haydock
Peter followed Jesus, but at a distance, for he was afraid. And so did another disciple. St. Jerome, and St. Chrysostom, and after him, Theophylactus, with some others, believe that this other disciple was St. John himself. (Calmet)