Jess and the twins and Mr. Rowan walked through the front door of Clive’s. Mom took one look at them and nearly dropped the coconut cake she was carrying. Jess knew they must look bad, streaked with dirt and covered with scratches from their run down the mountain.

“What on earth?” Mom cried, putting the cake on the counter and hurrying over to them.

Mom listened with wide eyes as they told her about the quake. She wrapped her arms around Jess and hugged her tight. Jess opened her mouth ready to tell her about Dad’s camera. But then Mr. Rowan announced the big news.

“We heard that St. Helens might erupt.”

Mom stared at him in shock.

“That’s ridiculous,” she said. “Who would say such a thing?”

A voice from the end of the counter called out.

“I would.”

Mom had been so busy fussing over Jess and the twins that she hadn’t noticed Dr. Morales, who’d walked in behind them. Mr. Rowan had invited him to join everyone at Clive’s, and he’d followed them down the highway in his car — that beat-up Toyota they’d spotted in the parking lot. Turned out that living through an earthquake made people fast friends.

“Tim here is a volcano expert,” Mr. Rowan said. “He works at a lab in Seattle.”

Mom looked Dr. Morales up and down with surprise. “You’re a scientist?”

With his overgrown curls and faded jeans, Dr. Morales looked more like a singer in a rock band than a person who worked in a laboratory.

“I’m not wearing my scientist uniform today.” Dr. Morales laughed. “But yes. I’ve been studying St. Helens for the past eight years.”

Mom sent Jess and the twins to get cleaned up. When they returned, they found Mom and the men sitting in a booth. There were mugs of hot chocolate waiting for Jess and the boys. There were no other customers in the diner, so Mom was free to sit with them.

“But I didn’t think St. Helens could erupt,” Mom said.

“I didn’t either,” Mr. Rowan said. “I figured it was the kind of volcano that’s dead, or whatever that word is …”

“You mean extinct,” Dr. Morales said. “But no. St. Helens is not extinct. It’s just been dormant, which means it’s been quiet.”

“But it’s always been so peaceful,” Mom said.

“It has been perfectly quiet, for one hundred and twenty-three years,” Dr. Morales said. “The last time it erupted was in 1857. But St. Helens is the most active volcano in the West. It has erupted dozens of times over the past few thousand years. There have been massive explosions, lava flows, avalanches, and mudslides. One eruption about five hundred years ago buried much of the valley under about two hundred feet of rock and ash and mud.”

“What about Cedar?” Mom asked.

“Cedar is up on a ridge. And I don’t think any of the eruptions have reached this far. It’s a safe place.”

“Good,” Mom said with a nervous smile. “I was about to start packing up.”

“Amazing that nobody around here knows about all this,” Mr. Rowan said, shaking his head.

“Actually, people did know,” Dr. Morales said. “Native Americans had been living here in the Cascades for about seven thousand years before the American settlers arrived. They knew St. Helens was dangerous and stayed away from it. They wouldn’t even fish from the lakes on the mountain. The Cowlitz tribe called this mountain Lawetlat’la. It means ‘mountain of fire.’”

The words seemed to hang in the air.

“What’s the most dangerous part of an eruption?” Mom asked.

“Lava?” said Sam, with just a little too much excitement.

“Lava is dangerous,” said Mr. Morales. “But around here, the bigger dangers are mudslides and rock avalanches. And I worry about the pyroclastic surge. That’s a wave of hot air that explodes out of the volcano. It’s truly devastating. That’s what happened in the eruption of Mount Pelée.”

“Never heard of Mount Pelée,” Mr. Rowan said.

None of them had.

“What happened?” Eddie asked.

“I don’t know if you want to hear about that,” Dr. Morales said. “It’s a grim story.”

“We do! We do!” Sam begged.

“Go ahead,” Mom said.

And so, as the hot chocolates grew cold, Dr. Morales told the story of the deadliest volcanic eruption in the twentieth century.