Ancient Greece, 480 BC. The Persians, before attacking Sparta, send envoys demanding its neutrality. At the same time, twelve-year-old Pleistarchus, son of King Leonidas, has left his family and is being trained in a camp in ancient Sparta, like all young Spartans. There, some try to assassinate him, but Pleistarchus manages to escape and with his cousin Agathocles, they search for the assassins.

Things get difficult when the second king of Sparta, Leotychidas, arrests and imprisons Leonidas, who wants to fight the enemy at Thermopylae. The two children and their group from the camp take action. The fate of the homeland is in their hands.

Will they succeed?
What is the secret that Leonidas is hiding well?