Mark 16:12
After that he appeared in another form unto two of them, as they walked, and went into the country.
Cross-references
Luke 24:23-35 gives the fuller account of the same Emmaus road appearance — the disciples' initial disbelief and later recognition of Jesus.
Luke 24:16 records the same Emmaus event: the two disciples' eyes were kept from recognizing Jesus. It fleshes out the brief summary in Mark.
Luke 24:35 concludes the Emmaus story with the two recounting how Jesus was known in the breaking of bread. This is the sequel to the appearance noted in Mark.
John 20:14 shows Mary Magdalene not recognizing Jesus initially. Both depict a post-resurrection appearance where the risen Jesus goes unrecognized at first.
John 21:4 has the disciples failing to recognize Jesus on the shore. Another instance of initial non-recognition after the resurrection, like Mark 16:12.