One day, some Pharisees and teachers of the law asked Jesus for a miraculous sign. Impress us, Jesus. Convince us, Jesus. We've heard rumors of your sleight-of-hand with water and wine at a wedding, your conjuring tricks with bread and fish, your stunts with demons and pigs. The word's out that you may be the Messiah: but we demand credentials. Give us a sign! Jesus rebukes them: "A wicked and adulterous generation asks for a miraculous sign! But none will be given it except the sign of the prophet Jonah." (Matthew 12:39).

A curious sign, this. Why not the sign of say, Elijah? Now there was a prophet--calling down fire from heaven, outrunning horses, staring down kings. Why not Isaiah? "Here I am Lord, send me." Daniel, he of courage in the Lion's Den? or Jeremiah the weeping prophet? But Jesus said Jonah: the rebel prophet, the sulking prophet, the prodigal prophet. Why Jonah? And what is his sign and why is it so important?