Elementary

In The Lost Hero, three demigods named Jason, Piper, and Leo made their first visit to Camp Half-Blood, where they inherited a quest:

Seven half-bloods shall answer the call,
To storm or fire the world must fall.
An oath to keep with a final breath,
And foes bear arms to the Doors of Death.

Annabeth is terrified. Just when she's about to be reunited with Percy - after six months of being apart, thanks to Hera - it looks like Camp Jupiter is preparing for war. As Annabeth and her friends Jason, Piper, and Leo fly in on the Argo II, she can't blame the Roman demigods for thinking the ship is a Greek weapon.