Morgan pulled a folded Paris newspaper from her windbreaker, and Collin dug a small lump of brownish-black mineral from his jacket.

"Pitchblende. It's what the Curies used to refine radium."

"Which one will work?" Morgan whispered to him.

"I don't know."

She wished they had heard the riddle. "Let's try the rock."

Collin crossed the invisible floor and dropped the pitchblende into the bottomless puzzle piece. Thunder bellowed around them, and the hole fused over and sealed shut.

Now, the answer! I must have the answer to the riddle.

"We didn't hear a riddle," Collin yelled. "Courtney may have heard your stupid riddle, but we didn't. So, where is she?"

Thunder rolled around the room, its rumble so loud Morgan was forced to cover her ears. Still she could hear the ominous, threatening voice.

They have no answer! They are mine, mine, all mine! boomed the Dark.

"Wait!" Morgan cried. "Give us a chance. At least tell us what the riddle is."

There are no second chances!

The dark, slithering snakes oozed through the invisible walls and floor, sliding closer and closer. Morgan wanted to run, but there was no where to go. The Dark was all around.

Like a boa constrictor, the darkness wrapped around her and Collin's feet. It grew tighter and tighter as it inched its way up their ankles.

"Think, Collin! What was it we said or did back in Paris that made the triangle appear?"

Collin slapped with little effect at the approaching Dark. "All I remember is Marie Curie's burned fingers and how she hoped radiation would kill cancer cells.

You're the one who knows about her experiments!"