Gower, an offscene narrator, enters to tell about the kingdom of Antioch, where king Antiochus and Antiochus's daughter are engaging in incest. Antiochus has kept suitors from marrying her by requiring that they answer a riddle correctly or die. Pericles, Prince of Tyre, tries his hand at the riddle. He is successful, but discovers that its answer reveals the incestuous relationship between father and daughter. Pericles doesn't reveal the truth, and Antiochus gives him forty days before his death sentence. But Pericles is sure Antiochus will want him dead for knowing the truth, so he flees back to Tyre. Antiochus sends an assassin after him.
In Tyre, Pericles worries that Antiochus will take some form of revenge, whether a military attack or an underhanded assassination attempt. Filled with melancholy, he takes the advice of Helicanus, his councilor, to travel for a while until Antiochus is no longer after him.
Pericles first goes to Tarsus, where king Cleon and his wife Dionyza bemoan the famine that has beset their nation. Pericles arrives with corn and saves them. But soon a letter from Helicanus calls Pericles back to Tyre, so he sets off.
On the way home Pericles is shipwrecked in a storm in Pentapolis. Some fishermen tell him about king Simonides's daughter, a lovely girl who will be married to whoever wins a jousting contest the following day. Pericles determines to enter the contest. Though his is the rustiest armor, Pericles wins the tournament, and dines with Simonides and his daughter Thaisa, both of whom are very impressed with him.
Meanwhile in Tyre, Helicanus reveals that Antiochus and his daughter have been burnt to death by fire from heaven, so Pericles can return. Other citizens want to crown Helicanus as king, but Helicanus insists they wait to see if...