He enters the city, spends the first day just getting himself deeper into the city, and then preaches his message: Yet forty days, and the city shall be overthrown. He doesn't have any particular care for the people of the city, and you can see it on his face. He's just going through the motions. Yes, he's warning the city of judgment, but he actually hopes they won't notice him.
But some do. Some laugh at him. "Everything is fine," they tell him. "We're a huge city, and no one and nothing could destroy us."
The preacher just laughs back. "Go ahead and believe that. I don't care."
"You stink," someone yells out. The preacher just ignores it and continues with his warning of judgment.
"Why do you stink so bad," they continue asking him. Finally, the preacher explains.
"It was a sailing accident," he tells them.
"A sailing accident? That can't be it, you're not just wet, you're covered in sulferous slime."
"I was swallowed by a great fish. It's really nothing. This city is going to be destroyed in --"
"Wait, you were swallowed by a great fish and survived?"
"Yes, but you're missing the important point. In forty days, this place will be smoldering ruins."
"How did that happen? Tell us!"
"Fine, I was told by God to come here and warn you about this destruction. I didn't want to do so, so I tried to sail off in another direction. God sent a storm and finally the sailors had to throw me off the boat to satisfy God's wrath, so the storm would stop. I got swallowed by the fish and brought by the fish to the shores of this city. Now I'm here preaching the message that God wanted me to preach in the first place, which is that you're going to be destroyed in forty days."
"But why didn't you want to come here and tell us? Why did you run away from your God's command?"
"Because I hate you guys. I want God to destroy you - and he will, in forty days."
"Why not just tell us this straight away?"
"Oh - no special reason."
"Come on, tell us. Why did you try to run away from giving us this message of destruction? We can see that you're happy God is going to destroy us."
The preacher just stands silently for a bit and then continues: "Yet forty days, and Ninevah shall be overthrown."
"Oh please tell us," the people beg him, "Why didn't you want to warn us?"
"Because I know God. He is a gracious God, and merciful, slow to anger, and of great kindness, and repents of the evil that he would do to those who deserve judgment when he sees repentance from sin."
Finally, the people who had only recently mocked this preacher, began to see what needed to be done. They sent to the king of the city and the king proclaimed repentance, fasting, and mourning for their sin in order to avert the judgment of God.
Jonah, our preacher, was not pleased by this result. He left the city and went to the east, setting up a small booth for himself to watch to see what would happen to the city. Perhaps God would destroy it as He did Sodom with fire from heaven.
But no judgment came. Jonah had been right about God: God was merciful to those who repent. Jonah was then even more unhappy and wished for death.
This is what I would call the world's worst evangelist. He had no desire for the good of those to whom he preached. He wanted them to be destroyed, and he only preached to them because God forced him to do so, at fish-point.
He was a cold-hearted man. He was more unhappy about a leafy gourd dying than he would have been about 120,000 children ("sixscore thousand persons that cannot discern between their right hand and their left hand") dying, not to mention the enormous amount of cattle in the city that would have perished as well.
But God used him powerfully. He brought a massive city - a city so big that it was a three days' journey across the city - to repentance and saved them from immanent judgment. It just goes to show what a great God our Lord is. He can use the world's worst evangelist to bring a wicked, pagan city to repentance.
Perhaps God is also calling you to preach the gospel to the lost. If so, do so knowing that God can use you. He can use you despite the worst failings you have - so don't be afraid to answer his call and preach.