Nico's POV

We caught the evening train to Grand Central. The three of us were in one compartment, along with a kind-looking elderly man reading a newspaper.

Theo yawned. I didn't blame the kid; he'd just taken up a burden no kid deserves.

"I need a nap," he said. "Could you wake me up when we get there?" His head drooped onto Percy's shoulder.

The old man had set his newspaper on the seat, and was now gazing at Theo with a strange glint in his eyes. I suppose I should have taken a hint from that, but I was too preoccupied by the day's events.

With nothing else to do, I began probing the people around me.

Being a son of Hades, I could detect souls and, with a bit of concentration, their emotions.

There was Theo, shocked and utterly exhausted from the day's revelations. Poor kid. I remembered how I'd felt when I found out I was a demigod.

There was Percy, who didn't seem all that worked up. He did these types of missions every week; this was kid stuff for him.

I concentrated on the old man next to me. As my probe reached him, I recoiled in shock. There was no soul there; only a gnawing, devastating hunger.

I was about to warn Percy, but, as if sensing my probe, the old man leapt up and began a horrific transformation.

"Cerastes!" Percy shouted, as the guise fell away to reveal a massive horned serpent. Theo jerked awake, and cowered behind Percy as the snake reared up.

Percy uncapped his pen to reveal his celestial bronze sword, and stabbed at the serpent, but it avoided the attack easily and darted forward. Percy managed to deflect the strike, but his sword was twisted from his hand and skittered under a seat.

I drew my Stygian iron blade (which I had decided to call The Grim Reaper, or in Greek, Charos – but more of that later) and swung at the snake. Even the touch of Stygian iron should have killed it, but it recovered quickly and stabbed at me with its horns. I jumped onto its head and cut it in half at the throat, and the serpent dissolved into gray dust.

Theo coughed. "What…what was that?"

"A monster," Percy said. "And trust me, you'll meet far worse soon enough."