Hazel frowned. "Why that ...

Hazel frowned. \
Hazel frowned. "Why that one?" "You don't see the ghost?" Frank asked. "Ghost?" Nico asked. Okay... if Frank was seeing a ghost that the Underworld kids couldn't see, something was definitely wrong.

Quotes from the same author

“It’s natural to feel fear. All great warriors are afraid. Only the stupid and the delusional are not.”
The main courtyard was filled with warriors - mermen with fish tails from the waist down and human bodies from the waist up, except their skin was blue, which I'd never known before.Some were tending the wounded. Some were sharpening spears and swords. One passed us, swimming in a hurry. His eyes were bright green, like that stuff they put in glo-sticks, and his teeth were shark teeth. They don't show you stuff like that in "The Little Mermaid.
Everybody was patting Nico on the back, complimenting him on his fighting. Even the Ares kids thought he was pretty cool. Hey, show up with an army of undead warriors to save the day, and suddenly you're everybody's best friend.
Back up shall we? When my brother, the crazy chicken warrior, turned into a falcon and went up the pyramid’s chimney with his new friend, the fruit bat, he left me playing nurse to two very wounded people—which I didn’t appreciate, and which I wasn’t particularly good at.
Aphrodite strikes again, huh? You're gonna be the best-dressed warrior in town, beauty queen.