What is the terrible secret buried beneath Cobra Island? Whatever it is, Starscream and Soundwave want it bad...bad enough to destroy Cobra Commander if he doesn't give it to them! Flint and the Autobots must prepare an all-out assault of the island themselves to prevent the villains' evil plans, but can the G.I. Joes count on Snake Eyes to help them...or will his vendetta against Firefly doom them all?