Identity Crisis!

Back at the palace, King Avimelech heard the good news, “Your majesty, we are pleased to announce that we have with us a stunning foreigner, fit for the king.”
“Bring her to me immediately!” the king commanded.
When Avimelech saw Rivkah, he had no doubts. He wanted her as a wife. But he suspected that perhaps she was already married to her so-called “brother” Yitzchak. He’d already heard about that other king, Paraoh, who was punished with nasty plagues when he tried to marry Avraham’s wife, Sarah. For that reason Avimelech did not want to take any chances!
One day, Avimelech observed Rivkah and Yitzchak talking and laughing together; they seemed friendlier than just brother and sister. He now suspected that they were indeed husband and wife!
“Yitzchak!” shouted Avimelech. “You lied to me. Rivkah is your wife, not your sister!”
“I had to say that,” Yitzchak answered, “otherwise I might have been killed!”
“What?! I, King Avimelech, the most important person in the royal kingdom, was about to marry a married woman?!” shouted the king. “That would have been my end! You should’ve warned me!”
A royal proclamation was immediately issued, “Hear ye! Hear ye! Anyone who dares even touch Yitzchak or his wife – will be put to death immediately!”