Who's the Naked Guy and Why Does He Matter?

One puzzle in the passion story is, Who’s the young man running through the garden without his clothes on?

Mark 14:51–52 says,

And a young man followed [Jesus], with nothing but a linen cloth about his body. And they seized him, but he left the linen cloth and ran away naked.

There are several options for who this is. But the best may be that it's the Gospel-writer Mark himself, who was in the city and an eyewitness to the Passion week proceedings. William Lane explains:

Several Fathers of the Church conjectured that the young man was Mark himself, who is known to have been a resident in Jerusalem (Acts 12:12) and in whose house, it was held by tradition, Jesus celebrated the [Passover] meal. If this is correct, Mark was an eyewitness to the transactions in Gethsemane. His primary purpose for including this vignette, however, appears to have been to emphasize the fact that all fled, leaving Jesus alone in the custody of the police. No one remained with Jesus, not even a valiant young man who intended to follow him. (The Gospel According to Mark, 527-528)

Jesus had no help at the cross from his followers. Only he could bring about our salvation, and so he had to work alone. Not even the young man Mark, with all the strength and vigor of youth, could help the Savior in his darkest hour.