Anderson’s Delights was situated in a long, low brick building at the end of a narrow street slicked with oil and foul-smelling puddles, next to the sludge of the Gowanus Canal, which wound through this section of Brooklyn like an enormous, green-scaled snake. At the end of the street, a homeless man wearing a battered felt cap, a pair of aviator’s goggles, and pants shredded halfway to his knees was rummaging through a trash bin, humming.

Pippa was glad that both Max and Sam had agreed to come. There was safety in numbers. And even though Pippa couldn’t stand Max, and tried her best to ignore her frequent complaints—(“Smells like a fart over here! What’s the big plan, anyway? You think if Anderson did steal the head he’s just gonna go ahead and cop to it?”)—she could see the sharp metal knives, sheathed in leather, glinting in the pockets of Max’s coat, and she was grateful for them. Especially as night was falling, and from the dark mouths of various doorways, men were watching them with sunken eyes.

The door to Anderson’s Delights was locked. Sam reached up and knocked carefully. Paint flaked off at his touch, and a crack appeared in the wood. He winced.

“Sorry,” he said.

“It’s not your fault,” Pippa lied.

They waited. Thomas shifted anxiously from foot to foot, tugging his hair, until it was standing straight up from his scalp. He never could stand still. Silence: no sound of footsteps, no murmur of voices. With each passing second, the light was draining from the sky. Pippa knew that meant curfew at the museum was rapidly approaching.

“Well,” Max said. “That’s that. No one’s home. Too bad and try again tomorrow.”

“Wait,” Sam said softly. “The light’s on upstairs. Look.”

He was right: above them, on the third floor, a light was glowing softly in the window. And it was flickering slightly, as though someone upstairs was passing in front of a lamp, walking back and forth in agitation.

By silent agreement, Pippa, Max, and Sam all turned to look at Thomas. Thomas sighed.

“All right, all right,” he grumbled. “I’m going.” In an instant, he was shimmying up a drainpipe—quickly, practically silent, except for the occasional squeak of his shoes or rattle of the metal pipe. Soon he became a small black shadow against the deepening twilight. And then, in less than a minute, he had reached the upstairs windows.

“What do you see?” Pippa called out softly.

“Nothing,” he called down. “Curtains are drawn. Give me a second.”

Like a spider, he flung himself from the drainpipe onto the narrow window ledge. Pippa gasped and unconsciously cried out as he teetered there for a second, windmilling his arms. But Thomas didn’t fall. He found his balance; dropped into a crouch; and, after fiddling with the latch, slid open the window and eased himself inside.

They waited in anxious silence for one, two, three seconds. Pippa expected at any second to hear an explosion of shouting, but there was nothing. Then Thomas’s head reappeared at the window.

“Come quickly!” he shouted. “Upstairs! Now! Hurry!”

Sam didn’t even hesitate. He drove a fist into the front door; with a tremendous boom it collapsed inward. Sam stepped aside and gestured politely for Max and Pippa to go before him.

“Thank you,” Pippa said, and passed into the shop.

The hall was carpeted and smelled like mildew and cat urine. To their right was a dusty glass door that obviously led to the shop; on it the words Anderson’s Delights had once been painted, but after several decades, only the letters And on Deli remained. A large sign that said CLOSED hung on the knob.

Directly down the hall was a narrow wooden staircase. Pippa raced toward it, and Max practically elbowed her out of the way.

“Move it,” she said.

Just as they had reached the second floor, Thomas appeared on the third-floor landing.

“Hurry!” he shouted again. His eyes were practically bulging out of his head. A door was open behind him, and Pippa caught a glimpse of dark green wallpaper and a ceiling crisscrossed with rough wooden beams.

“We’re coming—as—fast—as—we—can!” Pippa panted.

Max reached the third floor first. Pippa and Sam were right on her heels.

“This way.” Thomas’s face was stark white, as though someone had drained him of all his blood.

Together they piled through the open doorway, which led to Mr. Anderson’s private chambers. There was a fire burning cheerfully in the grate, and several lamps were illuminated. The room reminded him immediately of the museum. Every surface was cluttered with objects: a stuffed rearing king cobra, its fangs bared and hood extended; a carved African mask; a rusted saxophone. A mug of tea sat on a large mahogany desk, and a book was lying open on a squashy armchair.

And there was a body hanging from the rafters.

Pippa screamed. Sam shouted. And Max threw her knife. Quick as a flash, the blade whizzed through the air and severed the rope, slicing the body down from where it dangled.

The children ran to him at once. His face was the bruised purple of a storm cloud. A rope was knotted tightly around his fleshy neck. He was wearing an old pinstripe suit and a pair of patched leather shoes, and they knew at once they were staring down at the face of Mr. Anderson.

Sam kneeled beside him. Pippa hugged herself. She was suddenly freezing. For a minute, no one said a word.

“Is he . . . ?” Max asked finally.

Sam looked up at her. His dark eyes were hollows in his face. “Dead,” he confirmed.