Henry stared at the girl. “You’re the —”

“The person who has come to meet you.” The girl put a finger to her lips, even though the rest of the people on the roof were way over by the gargoyles. “We got your message,” she hissed, “and we agree to your exchange.”

“Really?” Henry’s mouth hung open. What kind of an international art-theft gang sent a teenaged girl to swap hostages for the most famous painting in the world?

“I trust you are ready to fulfill your promise?” She put her hands on her hips. Henry could see the sharp outline of the muscles in her arms and shoulders and wondered what she did to work out. Something other than playing video games, probably. Henry’s only really strong muscles were in his thumbs, so he was pretty sure she could kick his butt if she wanted.

“Well … yeah … but …” Henry looked around. “Where is everybody?”

“I came alone because we imagined you would be alone. One to one. That is usually how such things are done.”

“Okay. But …” Obviously, she had more experience than Henry because he had no clue how any of this stuff “usually” happened outside of Shadow Rogue Assassin. “How am I supposed to know you let them go?” he whispered.

“I will show you.” The girl turned and walked to the edge of the roof. Henry held the painting tight to his chest and followed her. The rain was picking up, running off the roof edges in streams. They squeezed between a big, drooly dragon sculpture and some killer-looking bird, and the girl pointed through the wire fence, toward a cluster of tiny people that hadn’t yet raised umbrellas to shield themselves from the rain and the view from above. They were huddled around a lamppost at the far end of the square, closer to the crypt than the cathedral.

When the girl stuck her hand through the fence and waved, the tallest of the group, a guy in a long charcoal-gray trench coat, waved back from below.

“That is the head of our organization’s security unit,” she told Henry. “Look closely … I think you will recognize his companions.”

Henry squinted through the rain and counted the others, and his heart raced. Aside from the tall guy, there were eight people — two short, skinny figures that looked about right to be José and Anna, one medium-size one that could be Hem, and five grown-up looking shapes that could easily be Aunt Lucinda, Anna’s mom, José’s parents, and Henry’s dad. In fact … yes! The second-tallest man had on a dark-colored jacket with white stripes and writing on the back. That was his dad’s police jacket! Henry wiped raindrops from his eyes and tried to get a better look.

But the girl’s hand landed on his shoulder wheeled him around. “We must finish this business and be done.” The girl’s bright blue eyes darted around the roof, where only a few die-hard tourists stood holding umbrellas for one another while their friends took photographs through the rain. “You will give me the painting, and I will signal for your friends to be released. You will see our man walk away from them, but before he does, he will tell them that you are on the roof, and they will acknowledge you. Then you must wait here.” The girl hadn’t taken her hand from Henry’s shoulder, and now he felt her grip tighten. “You will watch, and when I reach our man, we will walk away together and leave your friends to meet you below. Then — and only then — you may descend the stairs to meet them.” She let go of his arm.

Henry fought the urge to rub his shoulder; her grip was seriously strong. But the girl was smiling again. “It is how we must do things. You understand, my friend?”

Henry nodded, then turned to look for his dad again. The rain was still falling in a hazy gray curtain, but through it, he could see Anna and José, huddled together near one of the grown-ups — it looked like José’s mom — while the others stood hunched in the rain.

Henry turned back to the girl, held out the painting in its bag, and felt a quick stab of guilt at handing it over so willingly. But he had to do this, didn’t he? For his dad. “Sorry,” he whispered through the plastic.

The girl took the painting, carefully untied the top of the bag, peered inside, and quickly knotted the plastic again. She looked at Henry. “Remember. You will wait here until you see us leave,” she told Henry, her blue eyes cold as gargoyle stone. “If you don’t, our man has a gun under his coat and orders to use it.” Her face softened. “But I know that will not be necessary. We may be on opposing sides, but we can conduct ourselves with honor.” She held up the painting, and Henry saw for the first time a delicate serpent tattoo on the inside of her wrist. “I thank you for this,” the girl said. Then she turned and disappeared through the doorway that led to the long winding stairs.

Henry squeezed himself between two gargoyles and stared down at the square. He waved to make sure the tall man could see him waiting like he was told. The man raised his arm, and Henry felt a little better, knowing he’d seen him. Henry wished his dad would look up, but from the sound of things, he didn’t even know yet what was going on. Henry could only imagine how surprised he’d be when that girl got downstairs and told everybody they were free and Henry was up here, coming down to meet them so they could all go home.

Henry leaned forward as much as he could, until the wiry fence pressed into his forehead. He couldn’t see the side door of the cathedral, but he could see people coming into the square from somewhere. He counted to a hundred, and finally — there was the girl with the painting! She carried it in front of her like a birthday cake and walked right up to the man in the long coat. Henry saw them go over to his dad and the others — then point to his tower. They all turned and looked way up.

Henry waved like crazy, jumping up and down, and when they waved back, he felt the biggest, darkest, heaviest weight in the world lift from his chest. His dad and everybody gathered around the tall man, who looked like he was passing out candy or something. Then the tall guy turned to the girl, and she looked up at Henry and waved, and both of them started hurrying away through the square.

That was it! Henry whirled around and practically flew to the doorway that led back inside. He bounded down the twisty stairs two at a time until a bunch of tourists clogged up the stairway and he had to slow down. His heart felt like it might burst out of his chest and race past everybody to rush outside on its own.

Finally, the stairs took their last twist and light filled the doorway. Henry pushed out of the crowd and raced through the rain toward the lamppost. But he wasn’t even halfway there when he realized his dad — not just his dad, but everybody — was gone.

Henry ran to the lamppost — he was sure it was this one — the second to last — and turned in wild circles, looking for them. Where did they go? Why didn’t they wait for him?

Henry’s stomach dropped. What if the girl had lied? What if that guy in the long coat had forced them back to … to wherever they were being held as soon as Henry disappeared from his post on the roof?

“No! No!” Henry felt as if one of those gargoyles had taken a bite right out of his gut. But he couldn’t give up. Even if the Serpentine Princes had taken his dad and the others captive again, they were here a few minutes ago. Right here — and they couldn’t have gone far in the time it took Henry to race down those stairs.

He whirled around again, hoping for a glimpse of his dad or any of them — but the square was almost empty in the rain now. Even the pigeons had given up and found somewhere dry to beg for breadcrumbs.

Henry knew he didn’t have much time. After the girl waved, she and that guy in the long coat had set off across the square away from the river, toward the street on the other side of the crypt.

Henry took off running that way, sneakers splashing through puddles, his face hot and wet in the rain.

When he got to the edge of the square, he looked up and down the quiet sidewalks. Up by the cathedral, there were still a few die-hard people in line for the towers, but none of them were moving. Henry turned the other way and saw a couple of people disappear around a corner. Maybe he was hoping too hard, but it looked like one of them had a dark jacket with light-colored stripes.

Henry took off again. He’d spent so much time crouched all stiff behind that pillar in the cold rain that his knees felt like they might break with every thumping step. But he kept going, pumping his arms, nearly crashing into a waiter who’d stepped out of a café door with a pitcher of water.

“Sorry!” Henry jerked to the left and stumbled off the curb. A city bus blasted its horn. Brakes squealed. Henry leaped for the sidewalk and flailed into a café table. Silverware and plates went flying, clattering to the ground.

He weaved through the rest of the tables and turned the corner.

Yes! There it was! His dad’s blue jacket with the white reflective stripes. And now Henry could read the lettering on the back. Boston Police. It was him!

“Dad!” Henry screamed.

His dad was halfway up the block, hurrying along with one of the moms. Henry couldn’t tell if it was Anna’s or José’s but it didn’t matter.

“Dad! I’m here!” But the roaring rain and traffic must have drowned him out. “Dad!” Henry’s throat and chest were burning, but he pushed himself to run faster and finally caught up.

“Dad!” He reached out and caught the sleeve of the jacket, and the man whirled around to face him, arms raised in defense.

Henry stared.

It wasn’t his father.

The man barked something in French, but Henry only shook his head. It was Dad’s jacket, but it wasn’t Dad. This man’s face was longer, older, and marked with scars. His eyes were confused. “What you want?”

“I …” Henry couldn’t breathe. He felt like someone had punched him in the gut, like the time he’d flown off his sled and landed on his stomach and lay there with snow creeping down his collar. There was no air here, on this street corner. Henry bent over, hands on his knees, until he felt a big hand on his shoulder and jerked back up, gasping for air.

“Who are you?” Henry stared at the man, tears streaming down his face. “Where did you get that jacket?”

“I trade for it,” the man said defensively.

“Traded what?”

“I do a job for a pretty girl. She give me this jacket.” He looked at the woman next to him — about the height of José’s mom but with darker skin and shorter hair. “Her, too. And some others. We get two euro to stand in square and wave to boy on roof.” His eyes flashed with recognition. “Hey! You are roof boy!”

Henry wanted to throw up. If there had been anything in his stomach, he was sure he would have. “That’s my dad’s jacket.” It was all he could think to say.

The man shrugged. “They let me keep it.”

“Did you see where that girl went?” Henry asked.

The man shook his head. The woman said something in French, and the man nodded.

“She hear girl say something about Conciergerie. Maybe they go there.”

“Con-see-air-ju-ree?” Henry repeated. He whispered it to himself again. And again.

The man who was not Henry’s father raised his eyebrows, then turned and started down the street with the woman who was not José’s mom.

Henry watched them go, getting smaller and smaller until they were nothing but moving specks. But Henry felt even smaller than that. He’d given up the painting — his only hope of getting his father back — and watched it walk away while he stood on the roof like an idiot, waving to a bunch of stupid doppelgängers.

It seemed like the whole street was spinning. Henry could feel his heart beating in his forehead. He leaned against a brick building and slid down until he was sitting at the edge of the damp sidewalk.

We may be on opposing sides, but we can conduct ourselves with honor. He’d trusted the wrong person — again.

Now he didn’t know where his dad and the others were.

He didn’t even know where he was.

And he didn’t have anything left to give the Serpentine Princes in exchange for the hostages.

Henry pressed the heels of his hands into his eyes — hard — and tried to push back the tears. He was done. Game over, and the end music was playing. Unless …

Maybe he had one life left.

Henry took a deep, shuddery breath, unzipped Anna’s backpack, shoved aside José’s book of quotes, pulled out the notebook and a pen, and wrote down a single word. Henry had no idea what it meant or where it was or whether it meant anything at all. But it was the only thing he had to go on if he ever wanted to see his dad again.

Con-see-air-ju-ree.