Close to panic, Kari hopped her foot along the beam, only to have it forced back against the wall within moments. At the speed the beam was moving, she had a minute-less-before it completely disappeared and she was plunged into the pool with the remaining caiman… and the piranhas tearing at the flesh of its dead companion.

She still had the dagger in one hand, for all the good it would do her.

The dagger…

There must be something more, she realized. She had to do something with the dagger, not simply retrieve it.

“Throw me the flashlight!” she shouted.

“She’ll fall in!” Nina protested as Chase pulled back his arm.

“She’ll fall in anyway in a minute!” he shot back. “Kari! Ready?”

“Yes!”

He flung the flashlight. The brilliant light arced across the chamber like a falling star. Kari reached up with her wounded arm, and the light landed in her hand with a slap. Swaying to keep her balance, she brought it up, aiming the beam at the recess high above the other side of the pool. It was revealed as an alcove, a cube three feet to a side. Metal gleamed within, copper or gold, a foot-wide circular object like a shield standing up inside it.

Not a shield; a target.

There was only a meter of the beam still exposed, just seconds before it disappeared completely.

Kari turned and stepped onto it with both feet, snapping back her right arm to throw the dagger. The blade flashed through the torch beam-

It struck the target with a bang, dead center. The metal disc toppled backwards, disappearing from sight.

The beam stopped moving. With a creak of wood and straining ropes, the narrow drawbridge at the far end of the chamber fell, hitting the platform opposite with a whump.

Kari looked down. There was just enough of the beam still protruding from the wall for her to fit both her feet, if she turned them sideways.

She put her free hand against the wall for support, feeling very vulnerable. “Now what am I supposed to do?” she asked aloud.

As if in answer, there was a noise above her. A length of knotted rope, a chunk of wood weighing down its end, dropped from the ledge running along the wall.

Chase and Nina were already making their way to the bridge. “We’ll meet you on the other side!” Chase called as Kari gripped the rope and pulled on it, checking that it wasn’t about to break-or that it wasn’t booby-trapped itself. It seemed firm. Favoring her right arm, she climbed onto the ledge. It was only a foot across, but compared to what she’d just been standing on, it seemed as wide as a motorway.

Nina and Chase were waiting for her at the end of the drawbridge as she dropped down. “That was a hell of a throw,” said Chase as Kari slumped against the wall, exhausted. “How big was the target?” She held her hands a foot apart as Nina checked her makeshift bandage. “Bloody hell, I don’t think I could’ve made that. They weren’t kidding when they said it was a challenge of skill.”

“We’ve still got one more challenge to go,” Nina said.

“The Challenge of Mind? That sounds like your cup of tea, Doc. You up for it?”

She smiled nervously. “Do I have a choice?”

“How long have we got?” Kari asked Chase, voice tired.

“We’ve got… thirty-six minutes.” They all looked down the passage leading deeper into the temple. Even though it was no different from the others they had traversed, it somehow seemed more forbidding.

“Okay, then,” said Nina, standing straight with a defiance she definitely didn’t feel. “I hope my mind’s up to the challenge.”

FIFTEEN

Wary of traps, they made their way down the passage.

Something was troubling Nina, but she wasn’t quite sure what. It wasn’t just the adrenal aftershock of having narrowly escaped death. There was something else, a feeling, a certainty that she was overlooking some vital fact.

There was no time to think about it, though. Another chamber opened up ahead.

“Hold it,” said Chase, stopping at the entrance. He shone the light into the space beyond. “Smaller than the last one.”

Compared to the expansive pool chamber, this one was miniscule, only about fifteen feet across. As Chase moved the circle of light around, Nina saw that the walls were covered with markings-the same language as on the Atlantean sextant arm, and the entrance of the temple itself.

“Looks safe,” he announced, “but don’t quote me on that. Just be careful.” He stepped into the room, pausing as if expecting some hidden trap to be triggered, then signaled for Nina and Kari to follow. “Okay. So, Challenge of Mind. Go for it, Doc.”

“Right…” she said, taking the flashlight so she could examine the inscriptions on the walls. “Oh God! This could take days to translate!”

“We’ve only got thirty-three minutes to sunset. Think fast.”

“Nina, over here.” Kari had gone to the wall opposite the entrance. A stone block, unmarked by text, appeared to be a door, and next to it was what looked almost like…

“It’s a scale,” said Nina. “A weighing scale.” She aimed the beam beneath it. A trough was carved out of the stone, and inside it were a hundred or so lead balls, each the size of a cherry. “I guess we have to put the right number of balls into the scale. But how do we work out how many to use?” There was a lever by the scale’s copper pan; she reached for it, but Kari stopped her.

“I have a feeling that we only get one attempt,” she said, pointing up at the ceiling. Suspended above them was a large metal grid of foot-long spikes, ready to impale everyone in the room when it fell. Nina hurriedly pulled her hand away from the lever.

She flicked the light across the walls until she spotted large symbols carved over the closed door. They were arranged in three rows, one above the other, with groups of six different symbols in the uppermost one, five in the remaining two. Nina immediately recognized the first symbol. Groups of little marks like apostrophes…

“They’re numbers,” she announced. “It’s some kind of mathematical puzzle. Working out the answer tells you how many balls to put into the pan.”

“Is that all?” Chase sounded almost disappointed. “Christ, even I could do that. Let’s see… the top one, there’s three of those little dots, five upside-down Vs, seven bent-over Ls, two sideways arrows with a line under them, four backwards Ns and one backwards N with a line next to it. That’s 357,241. Doddle.”

“And you’d be wrong,” said Nina, managing a smile. “The numerical order is reversed from ours-the first symbol, the little dot, is actually the smallest number; each one of them is one unit. So the first number’s actually 142,753. It’s the same symbol from the river map on the sextant arm, and I know I’m right about it being a one, because otherwise we would never have found this place.”

“All right, smarty.” Chase grinned. “So the other numbers are… 87,527 and 34,164. So, what, we subtract them? That makes, uh…”

“Twenty-one thousand and sixty-two,” Nina and Kari said together, almost immediately.

Chase whistled, impressed. “Okay, so we don’t need a calculator. But there’s no way there’s twenty-one thousand balls in that trough.”

“What if it’s a combination of operators?” Kari suggested. “Subtract the second number from the first, then divide by the third?”

“Too complicated,” Nina said, staring at the numbers. “There’s no symbol suggesting that you need to perform different operations. Besides…” She frowned, working it out. “The result would be a fraction, and I don’t think putting one-point-six-two balls into the scale is likely to be the right answer.”

Chase winced. “Bloody hell. It hurts just thinking about doing that in my head.”

“The first number plus the third divided by the second is two-point-oh-two,” Kari suggested. “I doubt they would have calculated results down to one fiftieth accuracy. They may have rounded it to two…”