“It’s not just an Elsie charm,” Barclay said. “It’s the shell of a Ciansnail, and when you listen to it in an underwater river, it leads you to the heart of the Sea. Don’t you get it? That’s how Maedigan got to the Isle of Roane. That’s why she journeyed underneath the Sea.”

Tadg’s mouth slammed closed. For once he seemed unable to think of anything to argue.

“How do you know this?” Viola asked.

“Ulick and I were talking about it,” Barclay replied.

“If the Isle of Roane is real, and we can find it,” she said seriously, “then we should tell Runa.”

“Great,” Tadg grunted. “Let’s just add that to our list. If we wait until they finish questioning Ansley, we could be waiting here all night.”

“And what if… what if we’re wrong about Ansley?” Barclay asked.

Tadg and Viola both gaped.

“But you’re the one who told everyone she was studying the weeping tide,” Tadg said. “You’re the one who—”

“I know! I know.” Barclay already felt terrible about what he said. He didn’t need Tadg making him feel guilty too. “But something about it still feels wrong. And this time, if we tell the Guardian Keepers anything, I want to be sure.”

“So what are you suggesting?” Viola asked.

“We’ll leave now. We’ll find the Isle of Roane and come back. Then Runa and Cyril can be the ones to face Lochmordra. They can save the Sea.”

Barclay had expected it would take work to convince them—or worse, another argument. But to his shock, Tadg immediately said, “Barclay is right. We should go to the Isle of Roane so that we can be sure. And we can tell Runa about it when we come back.”

Viola still looked uncertain, but she was outvoted two against one. So, fifteen minutes later, the three of them snuck into the Planty Shanty. Barclay felt bad about stealing Polypops from Ansley—the very crime he’d once scolded Cecily for committing. But he would make it up to Ansley by finding the Isle of Roane and proving her innocence.

Soon they tied the slimy Polypops around their faces, climbed onto Mar-Mar’s even slimier back, and plunged beneath the ocean’s surface. With the Firenekkies to light their way, they retraced the familiar route to the underwater river they’d once raced on. The temperature on the seafloor was the hottest Barclay had ever felt it, and it wasn’t hard to guess the reason—the vents coughed up not just puffs of smoky water, but whole clouds. There hadn’t been an earthquake in some time, but Barclay worried the vents were now overactive beyond repair.

Mar-Mar halted at the riverbank.

“Come on,” Barclay told them. If they lingered here too long, they’d all be fried into fish sticks.

“How does the shell work?” Tadg asked.