Paul is under arrest for 2 years. Governor Felix is replaced by Porcius Festus. Paul is brought to an audience with Festus because the leaders from Jerusalem are still advocating that Paul be brought back to Jerusalem, hoping to ambush and kill him on the way. Paul refuses this and says “I am standing before the emperor’s tribunal; this is where I should be tried . . . I appeal to the emperor (10/11).” This is Paul’s right, as a Roman citizen, and so Festus orders him to be sent to the Emperor in Rome.
Before Paul is sent to Rome, Festus has King Agrippa and his wife Bernice, listen to Paul’s case and Paul takes this opportunity to preach the gospel.
Remember that the Holy Spirit has told Paul, several years before this, that he must bear witness to Jesus in Rome. Paul knows that he is going to Rome, I am equally certain that Paul did not expect to be going to Rome in chains.