Proteus (Πρωτεύς, Prōteus), the satyr play which originally followed the first three plays of The Oresteia, is lost except for a two-line fragment preserved by Athenaeus. It is widely believed to have been based on the story told in Book IV of Homer's Odyssey, where Menelaus, Agamemnon's brother, tries to return home from Troy and finds himself on an island off Egypt, "whither he seems to have been carried by the storm described in Agam.674".
The title character, "the deathless Egyptian Proteus", the Old Man of the Sea, is described in Homer as having been visited by Menelaus seeking to learn his future. Proteus tells Menelaus of the death of Agamemnon at the hands of Aegisthus and the fates of Ajax the Lesser and Odysseus at sea. Proteus is compelled to tell Menelaus how to reach home from the island of Pharos:
"The satyrs who may have found themselves on the island as a result of shipwreck . . . perhaps gave assistance to Menelaus and escaped with him, though he may have had difficulty in ensuring that they keep their hands off Helen."
The only extant fragment that has been definitively attributed to Proteus was translated by Herbert Weir Smyth:
"A wretched piteous dove, in quest of food, dashed amid the winnowing-fans, its breast broken in twain."
In 2002, Theatre Kingston mounted a production of The Oresteia and included a new reconstruction of Proteus based on the episode in The Odyssey and loosely arranged according to the structure of extant satyr plays.