We hurry back down to our makeshift campground and get everyone up and ready to continue as quickly and quietly as possible. I can tell the short rest was worth the delay. Everyone is moving faster—with less grouching.

Petraie leads the way to the door.

The oceanid smiles shyly before moving to the rock wall next to the door. She runs her fingertips over the stone, like a blind person reading braille. I can’t tell what she’s looking for. It all looks the same to me—one big mass of rough black surface—granite, maybe, or some kind of volcanic rock. Probably something that doesn’t exist in my world.

“What exactly is she looking for?” I ask the golden maiden.

“There is a hidden entrance,” she explains. “A side door of a sort, one that bypasses the security measures in place to guard the primary door.”

“Lucky for us someone thought to make this,” I reply.

The golden maiden gives me a sly grin. “Lucky for us someone on Olympus wanted undetectable access to the abyss for romantic assignations.”

“Someone?”

She shrugs, her shoulders squeaking quietly with the motion. “Rumor claims that Hera once had an affair with Alcyoneus.”

“The king of the giants?” I sputter. “No way.”

“Ahhh,” Petraie says, interrupting our gossip.

She pauses in front of an unexceptional-looking patch of black. Then, after clenching her hand into a fist, she presses it to the stone and pushes.

At first, nothing happens. I think maybe she’s wrong. Maybe it’s a different unexceptional patch of black. Then—slowly, with a rough scratching sound—the surface behind her hand pushes back into the wall.

I scan over my shoulder to make sure the monster group isn’t within earshot yet. Thane has his back to us, his shoulders rigid and his hands flexing in anticipation. I turn back to the door.

An instant later, a section of stone the size of my car slides silently back into the wall and then to the side, out of sight.

“This way,” the oceanid says, stepping inside the hidden passageway.

We’re following a water nymph into a secret entrance to Olympus. This might be the craziest thing I’ve done yet. I don’t know where this leads or what waits for us on the other side, but I know that bad things are coming from this side of the passage. As I follow Petraie inside, I reach down and pull out my daggers.

I feel better with a blade in each hand.

“There they are!”

I turn at the sound of the shout. The compass-wielding woman leading the monsters has just rounded the nearest rock formation and is pointing at us across the clearing.

“Run,” I scream, moving back to the entrance and bracing myself in a fighting stance. “Petraie, can we close the door?”

Thane takes a matching position at my side.

Something cold and wet touches my shoulder as the oceanid moves past me, brushing me in her hurry. As the monsters race toward the tunnel, Petraie frantically moves her hands over the rock on this side of the door.

“I cannot—” She shakes her head.

The first monster reaches us: a Teumessian fox that is quick as lightning. I spin left and focus all my strength in a powerful side kick to the chest. The fox flies backward, taking out the next fastest beast with the momentum.

Thane rushes out of the tunnel, pulling his sword off his back as he goes after the next wave of attackers.

“Any time now would be good,” I call out.

“I am hurrying,” Petraie insists.

I hold position at the door as Thane takes on a pair of ursa hybrids. A man with waist-length hair and a row of razor-like teeth gets past Thane. I’m about to give him a taste of my dagger when Greer spins out next to me, landing a solid kick to the side of the head. The man collapses, unconscious, on the ground.

“Nice,” I say.

Greer gives me a tight smile. “Thanks.”

“Yes!” the oceanid finally shouts. “Here.”

The door starts its slow, grinding slide back into place.

“Thane!” I shout. “Retreat!”

I stay in ready position, prepared to take on the rest of the monsters that are closing in, as Grace’s brother runs back inside. Then, with a puff of wind that sucks most of the air out of the tunnel, the door seals us in—and seals the monsters out.

There is a faint clicking sound before the glow from Thane’s flashlight illuminates the enclosed space. It looks like a tunnel carved into a mountain of the shiny black stone.

“Whew,” Greer says. “That was close.”

“Tell me about it.” I pull out my own flashlight and flick it on. “Let’s get through here before they figure out how to open that door.”

We wind our way through an unending black tunnel, our path illuminated by nothing more than our flashlights. Every so often I hear a high-pitched sound and I tell myself it’s Greer’s sneakers on the stone. She’s been squeaking every few steps since we started out yesterday. I just hope it’s not rats.

Petraie stops in front of me.

“The tunnel ends here,” she says.

“Please turn off your lights,” the golden maiden instructs, “and maintain absolute silence until I indicate the coast is clear.”

Thane and I shut down our flashlights, plunging us into even deeper black.

We wait, silent, in the dark tunnel as the golden maiden walks to the door at this end of the secret passage. The sound of a knock—faint and eerie in the darkness—echoes around us.