John the Baptist is rotting in prison, and while we do not know the exact nature of that state, I am sure the conditions were difficult. It may be that John was placed there by King Herod for his own safety, seeing as though John spent his days sending daggers of truth at the Powers who preferred the darkness. This safe keeping proved short-lived.
He is no longer John the Baptizer; rather, he is John the End-is-Near. It is dark, and I imagine John's surroundings began to corrupt his inner soul. Why am I here? What was I doing? Where did things go wrong? John sends his friends to Jesus. "Please see if He is the One. I want to know if this was worth it."
When they asked, Jesus responds "Look around you... and tell John what you see. What he has done has prepared the way, helped open doors, and the seeds he laid are beginning to take root.
'John, people do not know what to make of you; they gossip over you, and are not sure to bow to or avoid you. But when I see you, I see your forbearer Elijah.'
You go back and tell him."
Matthew 11:14