When Paul and Silas were walking to a place for prayer, the were stopped by a slave girl who had an evil spirit allowing her to tell the future. She also earnt lots of money for her fortune telling.
This girl followed Paul and Silas and shouted; "these men are the servants of the most high God who are teeling you the way to be saved"
This went on for many days until one day Paul got so irritated that he said to the spirit; "in the name of Jesus Christ i command you to come out of her" and at that moment the evil spirit left the girl.
When the owners of the girl knew that they couldn't make money anymore, they captured Paul and Silas and dragged them into the market place to face the authorities.
They told the officials that these men are Jews and are throwing our city into an uproar by teaching customs unlawful for us Romans to accept or practice. The officials responded in that Paul and Silas should be beaten and thrown into jail.
At midnight Paul and Silas were praying and singing hymns to God whilst the other prisoners were listening to him. Suddenly, such a violent earthquake that the foundations of the prisoners were shaken and at once all the prison cells flew open and chains were broken.