The Word of the Lord again comes to Jonah a second time, and the call is virtually identical. Get up. Go. And proclaim. This time, instead, of turning the other direction, the prophet actually goes where he is told to preach the message he has been sent with. Kind of. It seems as if Jonah preaches the bare minimum he can get away with. His sermon is only 5 words in Hebrew, and it mentions no word of repentance. It's possible that this is implied, or (based on the surrounding texts) it is possible that Jonah preaches reluctantly hoping to satisfy his vow to the Lord while not actually leading Nineveh to repent at all. He has just been the recipient of God's great mercy, and he now does everything in his power to ensure that Nineveh does not become a recipient of the same.
If we've seen anything in this book, however, it is that the Lord's will and plans will not be frustrated. If Jonah can subvert God's plan to call Nineveh to repentance, then God can subvert Jonah's subversion attempt and use his sermon anyway! The greatest and most unbelievable miracle that we see in this book is not the action of the great fish swallowing Jonah, it is the reaction of an entirely wicked, pagan city to turn unanimously in repentance to the Lord! The king calls for sackcloth and fasting across the whole city - even for the livestock! Jonah preaches hoping that Nineveh won't repent... and the Lord leads even the cows to repent! Jonah preaches that the city will be overturned (imagining fire and judgment raining down), and the Lord does just that! He overturns Nineveh! But not with hailstorms of judgment falling down but cries of repentance going up!
The Lord will not be frustrated.