Plot Summary and Background

Background
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......Before the Greeks go to war against the Trojans, the greatest of the Greek archers, Philoctetes, suffers a snakebite on his foot. While he is at sea on his way to Troy, his pus-ridden wound becomes so foul-smelling and his cries of pain so piercing that his shipmates abandon him on the island of Lemnos in the Aegean Sea. 

Summary
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......Sophocles' play begins in the ninth year of the Trojan War. At that time, the cunning Greek warrior Odysseus travels to Lemnos, a lonely island in the northern Aegean Sea, with Neoptolemus, the son of mighty Achilles, to find the greatest of the Greek archers, Philoctetes, and return with him to Troy. The Greeks desperately need Philoctetes, for a seer has warned that only his bow and poisoned arrows—weapons that once belonged to Heracles (Hercules)—can end the Trojan War. 
......After their arrival on the island, Neoptolemus and Odysseus discover the abode of Philoctetes, a cave in which he sleeps on leaves and eats from a crude wooden bowl. Philoctetes himself is not there. No doubt, Odysseus says, his is out foraging for food or for herbs to treat his wound.
......Odysseus realizes that Philoctetes will seethe with anger at the sight of any of the Greeks who abandoned him and may draw his deadly bow against them. So the ever resourceful Odysseus devises a scheme: Neoptolemus will approach Philoctetes and pretend to be a Greek warrior ill-used by Odysseus, then offer to return with Philoctetes to Greece. Honest Neoptolemus refuses at first, saying it is not in his nature to stoop to base trickery. But silver-tongued Odysseus tells him that it is his duty to sacrifice his individual ideals to benefit the welfare of the Greek community as a whole. Moreover, Odysseus says, Neoptolemus will be revered for ages to come as a wise and courageous warrior if he sets in motion a course of action that results in a Greek victory. Neoptolemus agrees to play the deceiver.
......All goes well when Neoptolemus meets with Philoctetes. However, after a time, Neoptolemus, is deeply moved Philoctetes' misery. Neoptolemus says (in the Thomas Francklin translation of the play):

............Alas! I pity him. Without a friend, 
............Without a fellow-sufferer, left alone, 
............Deprived of all the mutual joys that flow 
............From sweet society- distempered too! 
............How can he bear it? O unhappy race 
............Of mortal man! doomed to an endless round 
............Of sorrows, and immeasurable woe! 

......Consequently Neoptolemus confesses the truth to him, telling everything, but nevertheless tries to persuade Philoctetes to accompany him to Troy. When Odysseus appears, Neoptolemus declares asks forgiveness for his subterfuge and invites Philoctetes to come back with him to be healed and  to contribute to the Greek cause in the war. Philoctetes agrees to return—not because of the importunities of Neoptolemus but because of a mandate issued by Heracles, who appears deus ex machina and announces that Philoctetes and Neoptolemus must join forces to take Troy. When he returns to Troy, Heracles says, his wound will heal.

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