The next morning at dawn, Persephone and I were leaving Villa Pluto when someone slipped a note under the door. I ran and flung it open. No one was there. Only the whiff of a ghost.

“What is it, Hades?” asked Persephone.

“It’s from Medusa!” I exclaimed. We hadn’t heard from her in more than a year, and I’d been worried. I read it out loud:

“Greetings!
       Persephone, when you come back to earth today, will you bring a small bunch of Stygian riverwort? I’ll send someone to your apartment to pick it up. You’re a peach! My best to you, Hades!
       —Guess Who”

I scratched my head. “What in the Underworld can Medusa want with Stygian riverwort?” The stuff grows like a weed on the banks of the Styx. That’s the only place it grows.

“Beats me,” said Persephone. “But it’s easy enough to get.”

I drove Persephone to the river and waited while she picked some wort. Then I drove her up to her earthly apartment and carried in her mountains of luggage. We said our goodbyes. Then I drove swiftly back to my kingdom, where I had yet another problem to solve.

Lately, the ghosts had been complaining about Hermes. They said he was charging their relatives outrageous prices for driving them down to the Underworld on that rickety old bus of his. Being the god of business executives and thieves, Hermes always drives a hard bargain. But now things were getting out of hand.

I waited on the bank of the Styx that morning for Hermes. The little god may have been a thief, but he was punctual. His One-Way to the Underworld bus always arrived at XI o’clock on the dot. But that morning, XI came and went, and no bus arrived. XII o’clock, and still no bus. At quarter to I o’clock, I was boiling mad.

“Charon!” I called. “Has Hermes ever been this late before?”

“Never,” Charon said. “Usually shows up right on time. I hope nothing’s gone wrong,” he added. “A poor ferryman can’t make a living without any passengers, Lord Hades.”

“Spare me, Charon,” I muttered. The old river-taxi driver charged each ghost one gold coin to cross the River Styx. If a relative forgot to put a gold coin under a loved one’s tongue, that ghost would have to wait on the far shore forever! Charon never, ever brought anyone over for free.

I sat down on a rock. My stomach growled. I wished I’d brought a snack. At last I heard a rumble that wasn’t my stomach, and I saw the nose of Hermes’s ancient bus rounding the last curve of the Underworld Highway. With a squealing of brakes, the bus came to a stop beside the river. Hermes jumped out.

“Last stop!” Hermes called. He flapped the little wings on his helmet and sandals and flitted over the heads of the ghosts. “Only stop, actually. Every ghost out!”

I strode over to Hermes. “Where have you been? You’re almost two hours late.”

“Not my fault!” Hermes flapped higher, just out of my reach. “There was a crowd—”

“Don’t try to blame it on traffic,” I cut in. “The two of us are the only ones who ever drive on the Underworld Highway!”

“I don’t mean traffic,” Hermes said, still treading air just above my head. “You know how I pick up my passengers at Ghost Point?”

I nodded.

“Well, when I pulled up this morning, a huge crowd was gathered there. All my passengers wandered over to see what was going on, and I couldn’t get them rounded up and onto the bus.” Hermes fluttered over to some straying ghosts. “Stay in line for the river taxi!” he shouted.

“Will you land, Hermes?” I asked when he flapped back. “I’m getting a stiff neck from trying to look at you.”

Hermes fluttered to the ground and sat down on a rock. I sat down, too.

“The King of Argos was there,” he said. “He was in a terrible fury.”

“King Acrisius?” I said.

Hermes nodded. “His servants dragged a wooden chest to the seashore, and the king ordered them to put his daughter inside.”

“What?” I shouted, leaping to my feet. “Do you mean Danaë?”

Hermes shrugged. “I don’t know her name,” he said. “Or the name of her son, who was screaming his head off. At last a servant managed to force him into the chest with his mother.”

“Oh, no,” I cried.

“The queen was wailing up a storm,” Hermes went on. “She begged the king to let them out of the chest. All the people on shore were crying. Even my passengers were crying, which is unusual for ghosts.”

“Hermes! Quick! Tell me what happened!”

“Take it easy, Hades,” said Hermes. “The servants nailed the lid onto the chest. Then they carried the chest through the surf to a small boat. They king ordered them to row out beyond the waves and dump the chest into the sea.”

“Did they do this awful deed?” I asked.

Hermes nodded. “So you see, I couldn’t very well yank my passengers away—”

I didn’t wait to hear any more. I took off running. Minutes later, I was in my chariot galloping up the Underworld Highway. I tried phoning Po as I headed to earth, but he didn’t answer. I had to find him. He was my only hope of saving Danaë and Perseus.

I parked at Phaeton’s and astro-traveled to Po’s island.

“Po!” I cried, running up the walk to Cabana Calypso. “PO!”

A sleepy Po appeared on a palace balcony. “It’s the crack of afternoon, Hades.”

“It’s an emergency, Po!” I called. “You’ve got to hitch up your dolphins. Now!”

After a few minutes that seemed like hours, Po appeared at the palace door. “You wouldn’t believe the party I threw last night—”

“Later, Po,” I said, and I told him about Danaë and Perseus.

“Ghost Point?” he said. “Let’s go, bro!” We ran down to the dock, and soon we were speeding over the waves. My stomach was lurching with every bump, so I was glad when Po slowed his dolphins. He handed me the reins. “Hold the team steady, Hades. I’ll be right back.”

“Po!” I cried. “What—”

Po dove into the ocean. I heard a series of clicks, like seashells tapping each other. A minute later, Po rose to the water’s surface and pulled himself into the chariot.

“What were you doing?” I asked him.

“Sending a message to SNIT,” Po said. “Coded, of course. If anyone can find that wooden chest, SNIT can. We should be hearing from them any minute now, bro.”

Even as Po spoke, two heads popped up out of the water beside Po’s chariot.

“Special Agent Corius reporting, Lord Poseidon!” one said in a musical voice.

“Also Special Agent Merius!” said the other.

Both agents wore sea-blue swimming caps monogrammed with the letters SNIT.

“We have spotted the wooden chest,” said Special Agent Corius.

“It is barely afloat two nautreds off the island of Seriphos,” said Special Agent Merius.

“Seriphos, Seriphos,” said Po, thinking. “All right, it’s the best we can do. See that it washes safely ashore on the south side of the island. Near the home of Dictys, the fisherman.”

“It shall be done, Lord Poseidon!” said Special Agent Corius.

“The south shore,” Po repeated. “Not the north shore!”

“Yes, Lord Poseidon!” called Special Agent Merius. “The south shore!” And with that, the two disappeared into the sea.

For the first time since I’d heard Hermes’s tale, I felt a small flicker of hope.

Po gave a whistle. His dolphins sped off, and I had to grab on to the side of the chariot to keep from being tossed into the sea.

“We should make Seriphos in ten minutes!” Po shouted to me over the noise of his team. “We’ll watch and make sure that Dictys finds the chest and opens it.”

“What’s wrong with the north shore of Seriphos?” I yelled at Po.

“That’s where Dictys’s brother, Polydectes, lives,” Po yelled back. “Polydectes is the king of the island. He’s wicked, Hades. It would be better for Danaë and her son to drown than for them to end up in his hands. Look!” Po shouted, pointing toward a distant shore. “That’s Seriphos ahead. And hey, bro, there’s the wooden chest!”

I squinted into the distance, searching the sea. Then I saw it moving at a great speed atop the crest of a wave. Agents Corius and Merius had to be under the water, pushing it.

“Next wave and it’s beached,” said Po.

The trunk rose high on a breaker, which slid it gently up onto the shore.

Po grinned. “SNIT comes through again.”

A mortal who had been fishing in the surf ran over to the trunk. He bent down, inspecting it. He gave a sudden start. Then, with something from his tackle box, he pried off the lid. I held my breath, watching. Slowly, Danaë rose up out of the chest. She held Perseus in her arms. The boy was bawling loudly. Yes! They were alive!

“Wow,” said Po. “That boy can really wail.”

“Guess who his father is.”

“Fussing that loud?” said Po. “Gotta be Zeus.”

“Well, mission accomplished, Po,” I said. “Nice work.”

“It was, wasn’t it?” Po smiled. “I’ll send word to Dictys and let him know what’s what.” He revved up his dolphins. “He’ll take care of Danaë and Perseus.” He turned his chariot around, and we headed back to his palace.

“Make sure Dictys doesn’t tell anyone who they are,” I warned Po. “If King Acrisius finds out that Perseus is alive, he’ll send his henchmen to Seriphos to kill him.”

“You think they should go into SNIPP?” Po asked.

I shook my head. “Not necessary. Acrisius will never suspect that Danaë and Perseus survived his cruel plot. But what about Polydectes? Does Dictys confide in him?”

“No, Dictys knows what a creep his brother is,” Po told me. “Polydectes thinks he’s such a big cheese. Way too big to be king of only one little island. I hear he has a scheme to take over all the other islands around here.”

“How?” I asked.

“I hate to tell you, bro,” said Po. “It’s a nasty plot. He’s obsessed with having someone bring him Medusa’s head.”

“Her head?” I cried. “What?”

Po nodded. “He heard what Athena did to Medusa. How anyone who sees her face will be turned to stone. So he’s put out the word around here that he’ll pay handsomely for anyone who’ll go after Medusa, behead her, and bring him her head in a bag.”

“That’s abominable!” I cried.

“Really,” said Po. “I guess he figures he’ll row over to another island and ask to see the king. When the king shows up, he’ll pull Medusa’s head out of the bag. And bingo—the king’s a statue.”

“He wants to use Medusa’s head as a weapon?” I cried. “That makes my ichor boil!”

“Don’t worry about Medusa,” Po said. “She’s in no danger from ol’ Poly.”

“How do you know?” I said.

“Just trust me on this, bro,” said Po.

It took a while for my ichor to simmer down, and we didn’t say much for the rest of the trip. When we reached Po’s island, I asked him to let me know if there was ever trouble on Seriphos. Then I astro-traveled to my chariot and started for the Underworld. On the way, I thought about Po. He seemed very sure that Medusa was safe. But how could she be? Now she had a vicious goddess and an overambitious king trying to slay her. How I wished I could warn her!

When I got home, a letter from Guess Who was waiting for me.

Dear H,
       I’ve put the Stygian riverwort to good use!
       I hear you’re worried about me. Don’t be. I’ve never been better. E and R are fine, too. E has had some success with her photographs, and R is busy sculpting.
       We think of you often.
       —G.W.

was stunned. The only way Medusa could know I was worried about her was from Po. He must have contacted her right after I left him. Now I was worried. If word got out about where Medusa was, Athena would find her for sure. Obviously Po knew where Medusa was hiding. Could I trust my party-animal brother to keep his big mouth shut?