Trip nodded slowly. “Yes. I see. I know why Hecate sent you to me. Very well, son of Mars. Go find a way to fix my chariot. If you succeed, I will do all you ask. If not—”

“I know,” Frank grumbled. “My friends die.”

“Yes,” Trip said cheerfully. “And you’ll make a lovely patch of sorghum!”

FRANK STUMBLED OUT OF THE BLACK HOUSE. The door shut behind him, and he collapsed against the wall, overcome with guilt. Fortunately the katoblepones had cleared off, or he might have just sat there and let them trample him. He deserved nothing better. He’d left Hazel inside, dying and defenseless, at the mercy of a crazy farmer god.

Kill farmers! Ares screamed in his head.

Return to the legion and fight Greeks! Mars said. What are we doing here?

Killing farmers! Ares screamed back.

“Shut up!” Frank yelled aloud. “Both of you!”

A couple of old ladies with shopping bags shuffled past. They gave Frank a strange look, muttered something in Italian, and kept going.

Frank stared miserably at Hazel’s cavalry sword, lying at his feet next to his backpack. He could run back to the Argo II and get Leo. Maybe Leo could fix the chariot.

But Frank somehow knew this wasn’t a problem for Leo. It was Frank’s task. He had to prove himself. Besides, the chariot wasn’t exactly broken. There was no mechanical problem. It was missing a serpent.

Frank could turn himself into a python. When he’d woken up that morning as a giant snake, perhaps it had been a sign from the gods. He didn’t want to spend the rest of his life turning the wheel of a farmer’s chariot, but if it meant saving Hazel…

No. There had to be another way.

Serpents, Frank thought. Mars.

Did his father have some connection to snakes? Mars’s sacred animal was the wild boar, not the serpent. Still, Frank was sure he’d heard something once.…

He could think of only one person to ask. Reluctantly, he opened his mind to the voices of the war god.

I need a snake, he told them. How?

Ha, ha! Ares screamed. Yes, the serpent!

Like that vile Cadmus, Mars said. We punished him for killing our dragon!

They both started yelling, until Frank thought his brain would split in half.

“Okay! Stop!”

The voices quieted.

“Cadmus,” Frank muttered. “Cadmus…”

The story came back to him. The demigod Cadmus had slain a dragon that happened to be a child of Ares. How Ares had ended up with a dragon for a son, Frank didn’t want to know; but as punishment for the dragon’s death, Ares turned Cadmus into a snake.

“So you can turn your enemies into snakes,” Frank said. “That’s what I need. I need to find an enemy. Then I need you to turn him into a snake.”

You think I would do that for you? Ares roared. You have not proven your worth!

Only the greatest hero could ask such a boon, Mars said. A hero like Romulus!

Too Roman! Ares shouted. Diomedes!

Never! Mars shouted back. That coward fell to Heracles!

Horatius, then, Ares suggested.

Mars went silent. Frank sensed a grudging agreement.

“Horatius,” Frank said. “Fine. If that’s what it takes, I’ll prove I’m as good as Horatius. Uh…what did he do?”

Images flooded into Frank’s mind. He saw a lone warrior standing on a stone bridge, facing an entire army massed on the far side of the Tiber River.

Frank remembered the legend. Horatius, the Roman general, had single-handedly held off a horde of invaders, sacrificing himself on that bridge to keep the barbarians from crossing the Tiber. By giving his fellow Romans time to finish their defenses, he’d saved the Republic.

Venice is overrun, Mars said, as Rome was about to be. Cleanse it!

Destroy them all! Ares said. Put them to the sword!

Frank pushed the voices to the back of his mind. He looked at his hands and was amazed they weren’t trembling.

For the first time in days, his thoughts were clear. He knew exactly what he needed to do. He didn’t know how he would pull it off. The odds of dying were excellent, but he had to try. Hazel’s life depended on him.

He strapped Hazel’s sword to his belt, morphed his backpack into a quiver and bow, and raced toward the piazza where he’d fought the cow monsters.

The plan had three phases: dangerous, really dangerous, and insanely dangerous.

Frank stopped at the old stone well. No katoblepones in sight. He drew Hazel’s sword and used it to pry up some cobblestones, unearthing a big tangle of spiky roots. The tendrils unfurled, exuding their stinky green fumes as they crept toward Frank’s feet.

In the distance, a katobleps’s foghorn moan filled the air. Others joined in from all different directions. Frank wasn’t sure how the monsters could tell he was harvesting their favorite food—maybe they just had an excellent sense of smell.

He had to move fast now. He sliced off a long cluster of vines and laced them through one of his belt loops, trying to ignore the burning and itching in his hands. Soon he had a glowing, stinking lasso of poisonous weeds. Hooray.

The first few katoblepones lumbered into the piazza, bellowing in anger. Green eyes glowed under their manes. Their long snouts blew clouds of gas, like furry steam engines.

Frank nocked an arrow. He had a momentary pang of guilt. These were not the worst monsters he’d met. They were basically grazing animals that happened to be poisonous.

Hazel is dying because of them, he reminded himself.

He let the arrow fly. The nearest katobleps collapsed, crumbling to dust. He nocked a second arrow, but the rest of the herd was almost on top of him. More were charging into the square from the opposite direction.

Frank turned into a lion. He roared defiantly and leaped toward the archway, straight over the heads of the second herd. The two groups of katoblepones slammed into each other, but quickly recovered and ran after him.

Frank hadn’t been sure the roots would still smell when he changed form. Usually his clothes and possessions just sort of melted into his animal shape, but apparently he still smelled like a yummy poison dinner. Each time he raced past a katobleps, it roared with outrage and joined the Kill Frank! Parade.

He turned onto a larger street and pushed through the crowds of tourists. What the mortals saw, he had no idea—a cat being chased by a pack of dogs? People cursed at Frank in about twelve different languages. Gelato cones went flying. A woman spilled a stack of carnival masks. One dude toppled into the canal.

When Frank glanced back, he had at least two dozen monsters on his tail, but he needed more. He needed all the monsters in Venice, and he had to keep the ones behind him enraged.

He found an open spot in the crowd and turned back into a human. He drew Hazel’s spatha—never his preferred weapon, but he was big enough and strong enough that the heavy cavalry sword didn’t bother him. In fact he was glad for the extra reach. He slashed the golden blade, destroying the first katobleps and letting the others bunch up in front of him.

He tried to avoid their eyes, but he could feel their gaze burning into him. He figured that if all these monsters breathed on him at once, their combined noxious cloud would be enough to melt him into a puddle. The monsters crowded forward and slammed into one another.

Frank yelled, “You want my poison roots? Come and get them!”

He turned into a dolphin and jumped into the canal. He hoped katoblepones couldn’t swim. At the very least, they seemed reluctant to follow him in, and he couldn’t blame them. The canal was disgusting—smelly and salty and as warm as soup—but Frank forged through it, dodging gondolas and speedboats, pausing occasionally to chitter dolphin insults at the monsters who followed him on the sidewalks. When he reached the nearest gondola dock, Frank turned back into a human again, stabbed a few more katoblepones to keep them angry, and took off running.

So it went.

After a while, Frank fell into a kind of daze. He attracted more monsters, scattered more crowds of tourists, and led his now massive following of katoblepones through the winding streets of the old city. Whenever he needed a quick escape, he dove into a canal as a dolphin, or turned into an eagle and soared overhead, but he never got too far ahead of his pursuers.

Whenever he felt like the monsters might be losing interest, he stopped on a rooftop and drew his bow, picking off a few of the katoblepones in the center of the herd. He shook his lasso of poison vines and insulted the monsters’ bad breath, stirring them into a fury. Then he continued the race.

He backtracked. He lost his way. Once he turned a corner and ran into the tail end of his own monster mob. He should have been exhausted, yet somehow he found the strength to keep going—which was good. The hardest part was yet to come.

He spotted a couple of bridges, but they didn’t look right. One was elevated and completely covered; no way could he get the monsters to funnel through it. Another was too crowded with tourists. Even if the monsters ignored the mortals, that noxious gas couldn’t be good for anyone to breathe. The bigger the monster herd got, the more mortals would get pushed aside, knocked into the water, or trampled.

Finally Frank saw something that would work. Just ahead, past a big piazza, a wooden bridge spanned one of the widest canals. The bridge itself was a latticed arc of timber, like an old-fashioned roller coaster, about fifty meters long.

From above, in eagle form, Frank saw no monsters on the far side. Every katobleps in Venice seemed to have joined the herd and was pushing through the streets behind him as tourists screamed and scattered, maybe thinking they were caught in the midst of a stray dog stampede.

The bridge was empty of foot traffic. It was perfect.

Frank dropped like a stone and turned back to human form. He ran to the middle of the bridge—a natural choke point—and threw his bait of poisonous roots on the deck behind him.

As the front of the katobleps herd reached the base of the bridge, Frank drew Hazel’s golden spatha.

“Come on!” he yelled. “You want to know what Frank Zhang is worth? Come on!”

He realized he wasn’t just shouting at the monsters. He was venting weeks of fear, rage, and resentment. The voices of Mars and Ares screamed right along with him.

The monsters charged. Frank’s vision turned red.

Later, he couldn’t remember the details clearly. He sliced through monsters until he was ankle-deep in yellow dust. Whenever he got overwhelmed and the clouds of gas began to choke him, he changed shape—became an elephant, a dragon, a lion—and each transformation seemed to clear his lungs, giving him a fresh burst of energy. His shape-shifting became so fluid, he could start an attack in human form with his sword and finish as a lion, raking his claws across a katobleps’s snout.

The monsters kicked with their hooves. They breathed noxious gas and glared straight at Frank with their poisonous eyes. He should have died. He should have been trampled. But somehow, he stayed on his feet, unharmed, and unleashed a hurricane of violence.

He didn’t feel any sort of pleasure in this, but he didn’t hesitate, either. He stabbed one monster and beheaded another. He turned into a dragon and bit a katobleps in half, then changed into an elephant and trampled three at once under his feet. His vision was still tinted red, and he realized his eyes weren’t playing tricks on him. He was actually glowing—surrounded by a rosy aura.