Jupe scowled and pulled at his lip.
“It’s hard to believe,” he said, “but it is the only explanation that fits. Unless there are two people in this building who look exactly alike, Elmquist must be a wanderer. And I don’t think two identical people could exist in the same building for a period of months without someone realizing it.”
“Not with Mrs Bortz here,” said Prentice.
Pete, who had moved to the window, reported that Murphy’s nephew was leaving the building.
“Then we’re alone here.” Jupe stared at the cabinet where Prentice had concealed the ransom money. “A sack filled with cash,” he said. “Because it’s in the sack, the cash is invisible.” He began to smile, and suddenly his eyes sparkled.
“Hey, what is it, Jupe?” asked Bob, recognizing the signs of a mental breakthrough.
“Shall I tell you a story?” he replied.
“Oh, c’mon, Jupe!” groaned Pete. “Skip the build-up!”
“It’s a tale of murder,” said Jupiter, ignoring him. “A piece of fiction I read a long time ago. It’s about a murder that was committed with an invisible weapon.”
“Yes?” said Fenton Prentice.
“In the story,” said Jupe, “a man and his wife were having dinner with a friend in a closed room. The husband and the friend argued during the course of the meal, and the argument quickly became a raging quarrel. The men struggled, and the candles–which were the only light in the room–were knocked over. The wife then heard her husband cry out, and she felt something pull at her skirt. She screamed, and the servants came running. They found the husband dead, and the wife with blood on her skirt. The husband had been stabbed–but there was no weapon in the room. The servants searched and the authorities searched, but no one could find the weapon. At first they concluded that the husband had been killed by a demon.”
“How handy to live in an age when one could conclude a thing like that,” said Charles Niedland.
“The truth was,” said Jupiter, “that he had been killed by an invisible weapon–a knife made of glass. The murderer–the friend who had dined with the couple–had stabbed the husband in the dark and wiped the glass knife off on the wife’s skirt. He then put the knife into a pitcher of water that stood on the sideboard. It couldn’t be seen in the water.
“Mr Prentice, why would anyone poison Miss Chalmers?” asked Jupe. “Is there any reason, besides the fact that she swam in the pool every night?”
“Good heavens!” said Charles Niedland.
“And Mrs Bortz,” Jupe went on. “Certainly she’s a snoop, but no one tried to do her any harm–until she said she’d have the pool drained and cleaned. Mr Prentice, we have been looking for a crystal dog which is invisible because it is out in plain sight–just like that glass knife in the water pitcher.”
“The pool!” cried Bob. “It’s in the pool.”
Jupiter stood gleefully with his hands on his hips. “Tomorrow you are to ransom the crystal dog. Suppose we retrieve the dog today? It’s the perfect time. There’s no one but us in the building.”
“My word!” exclaimed Prentice.
Jupe grinned. “Bob,” he said, “you go and stand at the back gate and make sure no one comes in that way. Pete, you watch the street from the front gate.”
“And what are you going to do?” said Pete.
Jupe was headed out to the balcony, already unbuttoning his shirt. “I’m going swimming.”
Bob and Pete went to their posts, and Prentice and Niedland followed Jupe to the pool. He shed all of his clothes but his shorts and, shivering, slid carefully into the shallow end.
“Steady now,” said Prentice anxiously.
Jupe waded towards the deep end, scanning the blue and gold tiles on the bottom. When the water reached his chin he ducked under and let himself sink. Then, kicking out like a frog, he propelled himself forward just above the floor of the pool.
He kicked out again, and then he reached for something.
“He’s found it!” Fenton Prentice’s voice was an excited whisper. “By jove, he’s found it!”
Jupe shot to the surface. In his hand he held an object from which a string dangled. He paddled to the edge of the pool and offered his prize up to Fenton Prentice.
“The Hound!” exclaimed the old gentleman. He took the sculpture and turned it over and over in his hands. It was a strangely beautiful figure of a heavily muscled dog with a square massive head. The wide round eyes were rimmed with gold, and gold froth flecked the crystal jowls. The sculpture was about six inches tall, from the bottom of the glass base to the tips of the dog’s ears. Between the feet of the animal was a human skull. Someone had tied a long piece of gilt cord around the dog’s middle.
“So simple,” said Jupiter. “The burglar didn’t even have to get into the pool. He lowered the Hound by that cord until it touched bottom, then let go. The gold cord was invisible against the random pattern of blue and gold tiles.
“Ingenious!” said Charles Niedland.
“May I have it back?” said Jupiter to Fenton Prentice.
“What?” said Prentice.
“I said, may I have it? I want to put it back in the pool.”
“Why on earth?”
“Because tonight the burglar may come back for the dog. He’s still expecting you to deliver the ransom tomorrow. We’ll return the invisible dog to its hiding place, and then we’ll watch the TV monitor–and find out who the burglar is!”
“I see.” But Fenton Prentice still held on to the dog.
“It makes sense, Fenton,” said Charles Niedland.
“But . . . but the dog could be injured, chipped, broken!”
“So far the burglar has been careful with it,” said Jupe. “I think he’ll stay careful.”
Fenton Prentice sighed and handed the crystal statue back to Jupe, who lowered it slowly into the water where he’d found it.
“I need a towel,” he said. “I don’t want anybody to know I’ve been in the pool. There mustn’t be any wet footprints on the deck.”
Charles Niedland bounded up the stairs and was back in a minute with several towels and a thick bath mat. Jupe climbed out of the pool on to the mat and hastily dried himself.
“Hassell’s coming!” Pete had darted in from the front gate.
“Get Bob!” ordered Jupe as he scooped up his clothes. “Quick! Everybody upstairs.”
As the group dashed into Prentice’s apartment, footsteps could be heard on the stairs that led from the street to the gate. Jupe nicked on the TV monitor and watched Alex Hassell stalk stiffly across the court and go into his own apartment.
“He didn’t even look at the pool,” said Jupe.
“Why should he?” asked Bob.
“Because, even though I was very careful, the water is slightly disturbed. It always is when someone goes into a swimming pool. It won’t be completely still again for some time.”
“Then Hassell isn’t our burglar,” decided Pete.
“Either he isn’t our burglar, or he’s afraid he’s being watched. He might notice the pool and be too smart to react visibly. We’ll see.”
In the courtyard, cats began drifting in. They gathered in a silent semicircle around Alex Hassell’s door and sat, waiting. Presently Hassell came out with some dishes. The cats ate as he watched. He petted them and talked to them; then they departed. In a short time Hassell himself left the building.
The boys helped Fenton Prentice cook dinner and they all ate, with one of the Investigators constantly watching the TV monitor. At eleven, the lights in the courtyard went out.
Pete got his jacket out of the closet. “Here we go again with the night watch on the balcony.”
“I think I’ll watch with you,” said Jupe.
Bob stood up. “Count me in, too. Tonight something should happen–and I want to see it!”
17
The Shadow Acts
AT MIDNIGHT, the gate clicked open. The slim, slouching shape of Sonny Elmquist appeared below and went into his apartment. A light shone out briefly from Elmquist’s windows and then went out.
The watchers on the balcony waited.
A door opened and closed. The Three Investigators could see someone moving below them!
Pete gripped Jupe’s arm.
The shadowy shape drifted slowly to the shallow end of the pool. It slid into the water silently and moved forward, barely making ripples.
Suddenly the Three Investigators heard the person take an audible breath. He dived under the surface with a small splash. Then a beam of light shone under water. Whoever had gone into the pool had a waterproof flashlight. Its beam swept back and forth across the bottom of the pool.
A hand appeared in the beam of light. It stretched down and closed around an invisible object–the transparent Carpathian Hound!
The person surfaced and climbed out of the pool. A moment later a door opened and closed again.