The left side of my brain finally took over, allowing the mental gear to tumble into place.

"Jesus, how could I have been so fucking blind!"

I clicked on the sonar array program, rewinding to the system's passive sonar recordings. The computer must have captured the monster's sonar signature earlier that evening, but I'd been too preoccupied to listen.

Locating the recording, I turned up the volume.

Blee-bloop… Blee-bloop… Blee-bloop… Blee-bloop …

My heart raced, my head swimming with the implications.

Blee-bloop… Blee-bloop… Blee-bloop… Blee-bloop …

"It is… it's the Bloop! How could I not see it? It was there, it was right there in front of me the whole time!"

Brandy stirred. "Zack? What's wrong?"

I leaped onto the bed. "I know, Brandy! I know what Nessie is! She's not a plesiosaur, she's not a dinosaur, she's not a sturgeon or a myth or even an ancestor of modern-day whales, but she is a precursor!"

"A precursor?" Brandy sat up in bed. "A precursor of what?"

"The Anguilla eel!"

"An Anguilla? Nah… how can that be? She's so big."

"It's Nature's way. The ancestors are always larger. Then evolution takes over, it adapts, it makes adjustments, based on environment and competition, and the availability of prey. Anguillas and these… these Guivres, for lack of a better name—they're both born in the Sargasso Sea."

"How dae ye know that?"

"Because Nessie's not the last Guivre, and she's not a mutant, her kind's not extinct! Her species still inhabits the Sargasso. The Navy tracked them on sonar, called them bloops, but no one knew what they were. It was the bloops, I mean the Guivres, that attacked the giant squid. Like Anguilla, they spawn in the Sargasso Sea, then the young drift on ocean currents back to Britain and the rest of Europe. Being smaller, Anguilla could follow the Ness River into the Loch every spring. The larger females leave in autumn when they're old enough to spawn, but their big cousins, these Guivres, they were always too large to access the Loch through the river, instead they followed the Ness Aquifer—an undiscovered, underground river that flows from Loch Ness into the North Sea. But the passage collapsed seventy years ago when the A82 was dynamited—"

"Trappin' Nessie?"

"Yes!" I paced the room, my mind on fire. "She must be a female. Female Anguilla grow really big, much bigger than the males, so the same probably holds true for Guivres. They leave Loch Ness when they're ready to spawn, returning to the Sargasso Sea. But Nessie's trapped, it's screwed up her biological clock. She can't spawn in freshwater, her DNA won't allow that, so instead, she just kept growing, getting larger and larger. She's a mutant, Brandy, and now she's become dangerous, her brain filled with lesions caused by an oil leak."

"Oil? I dinnae understand?"