Euripides 
Rhesus [EPUB ebook] 

In the middle of the night Trojan guards on the lookout for suspicious enemy activity sight bright fires in the Greek camp. They promptly inform Hector, who almost issues a general call to arms before Aeneas makes him see how ill-advised this would be. Their best bet, Aeneas argues, would be to send someone to spy on the Greek camp and see what the enemy is up to. Dolon volunteers to spy on the Greeks in exchange for Achilles’s horses when the war is won. Hector accepts the deal and sends him out.