Alcibiades (25.6-25.7)

But without his knowing it, it was a case of traitor dealing with traitor. For Astyochus was much in awe of Tissaphernes, and seeing that Alcibiades had great power with the satrap, he disclosed the message of Phrynichus to them both. Alcibiades at once sent men to Samos to denounce Phrynichus. All the Athenians there were incensed and banded themselves together against Phrynichus, who, seeing no other escape from his predicament, attempted to cure one evil by another and a greater.

He sent again to Astyochus, chiding him indeed for his disclosure of the former message, but announcing that he stood ready to deliver into his hands the fleet and army of the Athenians. However, this treachery of Phrynichus did not harm the Athenians at all, because of the fresh treachery of Astyochus. This second message of Phrynichus also he delivered to Alcibiades.