Eidothea, known as Eido or Theonoe in some traditions, was the daughter of the sea god Proteus who told Menelaus and his wife Helen how to get home to Sparta when they were stranded in Egypt after the Trojan War.
Were Eidothea and Theonoe the same person?
Homer’s Eidothea and Euripides’ Theonoe (or Eido) appear to have corresponded to more or less the same figure, with Euripides’ Theonoe being a later reinterpretation of Eidothea.
How did Eidothea help Menelaus and Helen?
In the Odyssey, Eidothea found Menelaus when he was stranded on the island of Pharos just off the Egyptian coast and told him what he needed to do to get home to Sparta. In a later tradition, known from Euripides’ Helen, Eidothea is called Theonoe and also helps Menelaus and Helen leave Egypt, though under different circumstances and in a different way.