A.T. Robertson Commentary John 21:20

"Peter, turning about, seeth the disciple whom Jesus loved following; who also leaned back on his breast at the supper, and said, Lord, who is he that betrayeth thee?" — John 21:20 (ASV)

Turning about (επιστραφεις). Second aorist passive participle of επιστρεφω, old verb, here a sudden turning round (ingressive aorist). For the simplex verb στρεφω see 20:14,16.

Following (ακολουθουντα). Following both Jesus and Peter, perhaps having heard the graphic dialogue above.