Before the Play
- Arbaces, the King of Iberia, has defeated Tigranes, King of Armenia, in single combat, putting an end to many long years of war.
During the Play
- Victorious Arbaces declares that the only ransom Tigranes must pay is to marry Arbaces’ younger sister Panthea. Arbaces hasn’t seen his sister since he left Iberia when she was nine years old, but he promises Tigranes that she is peerless in beauty and grace.
- Tigranes counters that he would rather pay “worlds of ransom” than marry Panthea; Arbaces demands that Tigranes journey to Iberia to meet Panthea before refusing her. Tigranes agrees.
- Mardonius, an Iberian Captain, urges Arbaces to check his hasty temper.
- Arbaces learns that his mother was foiled in her latest attempt to take his life.
- Tigranes entreats his secret beloved Spaconia to travel before him to Iberia and lobby Panthea to refuse the marriage.
- In Iberia, Lord Protector Gobrius and the Queen Mother Arane engage in a cryptic exchange and he cautions her to cease her treasonous plotting.
- Captain Bessus arrives in Iberia to report on Arbaces’s success and deliver Spaconia, but focuses primarily on his own role in the conflict.
- Having seen Panthea, Spaconia is afraid that Tigranes will fall in love with her on first sight. Spaconia confesses to Panthea Tigranes’s desire not to be wooed and urges her help in the matter. Panthea swears she will not stand between the pair.
- The Iberian citizens welcome Arbaces home. After years apart, Arbaces cannot believe that the young woman in front of him is his sister. He falls in love with her.
- Panthea is confused and distressed by her brother’s erratic behavior.
- Tigranes also falls in love with Panthea despite his guilt over breaking his vow to Spaconia.
- Spaconia sees the change in Tigranes’s affections and is distraught.
- Arbaces sends Tigranes to prison.
- The boastful Bessus, his honor newly restored by his actions in war, is dismayed to be challenged to several duels.
- Arbaces is wracked with guilt over his incestuous love for his sister.
- Potential damnation ensues.