The animals slowed as they approached. Probably, they were confused about how to kill us through the trees. Yales were aggressive, but they weren’t hunters. They didn’t use fancy maneuvers to corner and defeat prey. If somebody got in their territory, they just charged. The trespassers died or fled. Problem solved. They weren’t accustomed to intruders who played keep-away.

We edged around the oaks, doing our best to stay opposite the beasts.

“Nice yales,” I sang. “Excellent yales.”

The yales did not seem impressed.

As we shifted perspective, I spotted something about thirty yards beyond the animals: a cluster of washing-machine-size boulders in the tall grass. Nothing terribly dramatic, but my keen ears picked up the sound of trickling water.

I pointed out the rocks to Meg. “The cave entrance must be there.”

She wrinkled her nose. “So do we run for it and jump in?”

“No!” I yelped. “There should be two streams. We have to stop and drink from them. Then the cave itself…I doubt it will be an easy descent. We’ll need time to find a safe way down. If we just jump in, we might die.”

“These harvards aren’t going to give us time.”

“Yales,” I corrected.

“Same difference,” she said, totally stealing my line. “How much do you think those things weigh?”

“A lot.”

She seemed to run that through her mental calculator. “Okay. Get ready.”

“For what?”

“No spoilers.”

“I hate you.”

Meg thrust out her hands. All around the yales, the grass went into overdrive, braiding itself into thick green ropes that wrapped around the beasts’ legs. The creatures thrashed and bellowed like gargling foghorns, but the grass continued to grow, climbing across their flanks, entangling their massive bodies.

“Go,” Meg said.

I ran.

Thirty yards had never seemed so far.

Halfway to the rocks, I glanced back. Meg was stumbling, her face glistening with sweat. It must have been taking all her strength to keep the yales entangled. The beasts strained and spun their horns, slashing at the grass, pulling against the sod with all their might.

I reached the pile of rocks.

As I’d suspected, from side-by-side fissures in the face of one boulder, twin springs gurgled, as if Poseidon had come by and cracked the stone with his trident: I want hot water here, and cold water here. One spring bubbled diluted white, the color of nonfat milk. The other was as black as squid ink. They ran together in a mossy streak before splattering against the muddy ground.

Beyond the springs, a crevasse zigzagged between the largest boulders—a ten-foot-wide wound in the earth, leaving no doubt as to the presence of the cavern system below. At the lip of the chasm, a coil of rope was tied to an iron piton.

Meg staggered toward me. “Hurry,” she gasped. “Jump in.”

Behind her, the yales were slowly ripping through their grassy bonds.

“We have to drink,” I told her. “Mnemosyne, the Spring of Memory, is black. Lethe, the Spring of Forgetfulness, is white. If we drink both at the same time, they should counteract each other and prepare our minds—”

“Don’t care.” Meg’s face was now as white as the waters of Lethe. “You go.”

“But you have to come with me! The Oracle said so! Besides, you won’t be in any shape to defend yourself.”

“Fine,” she groaned. “Drink!”

I cupped one hand in the water of Mnemosyne, the other hand in the water of Lethe. I gulped them down simultaneously. They had no taste—just intense, numbing cold, the sort that hurts so badly you don’t feel the pain until much later.

My brain began to swivel and corkscrew like a yale horn. My feet felt like helium balloons. Meg struggled with the rope, trying to wrap it around my waist. For some reason, I found this hysterical.

“Your turn,” I giggled. “Drinkie, drinkie!”

Meg scowled. “And lose my wits? Nuh-uh.”

“Silly willy! If you don’t prepare yourself for the Oracle—”

In the meadow, the yales ripped themselves free, peeling off several square yards of turf from the ground.

“No time!” Meg lunged forward, tackling me around the waist. Like the good friend she was, she sent me tumbling over the ledge and into the black void below.

Feeling groovy, I’m

Drowning, freezing, snake surfing

Life is good, Batman!

MEG AND I PLUMMETED through the dark, our rope unspooling as we bounced off one rock then another, my clothing and skin getting brutally scraped away.

I did the natural thing. I screamed, “WHEEEEEE!”

The rope snapped taut, giving me the Heimlich maneuver so violently I almost coughed up my appendix. Meg grunted with surprise and lost her grip on me. She fell deeper into the darkness. A heartbeat later, a splash echoed from below.

I laughed, dangling in the void. “That was fun! Again!”

The knot unraveled at my waist, and I plunged into frigid water.

My delirious state probably saved me from drowning immediately. I felt no need to struggle, thrash, or gasp for breath. I floated down, vaguely amused by my predicament. The sips I had taken from Lethe and Mnemosyne battled in my mind. I couldn’t remember my own name, which I found extremely funny, but I could recall with perfect clarity the yellow flecks in Python’s serpentine eyes as he sank his fangs into my immortal biceps millennia ago.

Beneath the dark water, I shouldn’t have been able to see anything. Nevertheless, images floated in and out of my vision. Perhaps this was the effect of my eyeballs freezing.

I saw my father, Zeus, sitting in a patio chair by an infinity pool at the edge of a terrace. Beyond the pool, an azure sea stretched to the horizon. The scene would have been more fitting for Poseidon, but I knew this place: my mother’s condo in Florida. (Yes, I had one of those immortal moms who retired to Florida; what can you do?)

Leto knelt at Zeus’s side, her hands clasped in prayer. Her bronze arms glowed against her white sundress. Her long golden hair zigzagged down her back in an elaborate ladder weave.

“Please, my lord!” she implored. “He is your son. He has learned his lesson!”

“Not yet,” Zeus rumbled. “Oh, no. His real test is yet to come.”

I laughed and waved. “Hi, Mom! Hi, Dad!”

Since I was underwater and most likely hallucinating, my words should not have been audible. Nevertheless, Zeus glanced over and scowled.

The scene evaporated. I found myself facing a different immortal.

Floating before me was a dark goddess, her ebony hair wafting in the cold current, her dress billowing around her like volcanic smoke. Her face was delicate and sublime, her lipstick, eye shadow, and mascara all expertly done in shades of midnight. Her eyes gleamed with absolute hatred.

I found her presence delightful. “Hi, Styx!”

Her obsidian eyes narrowed. “You. Oath-breaker. Do not think I have forgotten.”

“But I have!” I said. “Who am I again?”

In that moment, I was absolutely serious. I knew this was Styx, goddess of the Underworld’s most important river. I knew she was the most powerful of all water nymphs, eldest daughter of the sea Titan, Oceanus. I knew she hated me, which wasn’t surprising, since she was also the goddess of hatred.