We must get out before it’s too late!” Nancy called frantically.

The old man looked at the girl as if she were a ghost. “Nancy Drew! How did you get here? ”

“Never mind! We’re all in danger! ” Nancy cried. “Follow me up these steps! ”

Grumper snarled at the girl and barred the man’s path.

“You’ll have to fight me to get past here! ” he chortled. “Anyway, it’s too late! I can hear the water now! ”

Hopping about gleefully, the crazed man swung the bell. A. H. pushed him aside and dashed for the steps. Grumper laughed wildly.

“The waters will swirl to the very top of the cave stairs! ” He chuckled. “And the door to the lab locks itself from the outside.”

“Quick, you fool! ” Hendrick cried. “Give us the key! ”

“I threw mine away! We’ll all die here together! ”

Nancy and A. H. were frantic. Although escape seemed impossible, they started up the steps. Grumper trailed them, gloating over his enemy’s predicament. When they reached the top, A. H. stood gasping for breath as Nancy turned to Grumper.

“Why don’t you try to save yourself? ” she urged, hoping that he might know some other way out of the cave. “Your boss didn’t ask you to give up your own life.”

“That guy who calls himself Monsieur Pappier and Mr. James and half a dozen other names will no longer be my boss.” Grumper laughed mirthlessly. ”His real name is Harry Tyrox, and he’s a trickster and a cheat. Why, he even tried to steal my jeweled bell and sell it to Hendrick. When I found him out, he bargained with me to share the money I’d get for it. But I’ve outwitted him! I’ll take the bell with me to the bottom of the sea! ”

“So that’s what upset you? ” Nancy managed to speak soothingly as she tried desperately to gain their freedom. “You thought Tyrox intended to take the bell. Just lead us out of this trap and we’ll have the police put that man behind bars.”

“It’s no use, ” Grumper replied in a calmer voice. “I have no key and the secret door is locked.”

“Then we really are trapped here? ” Nancy asked, losing heart for the first time.

“Yes, we’re trapped. I’m sorry you have to go, too. When you first came to the cave I tried to frighten you away, and later that day I hoped to scare you with sleeping-gas fumes. But you wouldn’t leave me alone, so you must suffer too.”

At that instant in the cavern below they heard a faint, gurgling sound.

“The water is starting through, ” Grumper said. “In a moment it will come with a rushl”

In desperation Nancy pounded on the heavy secret door, but succeeded only in bruising her fists.

“Help! Help! ” she called weakly.

Then suddenly Nancy wondered if her mind was playing a cruel trick on her. From behind the door had she heard footsteps and a muffled voice?

CHAPTER XX