“Extraneous biological matter.”

“You mean the green-pigmented structures?”

“Yes.”

“Membrane-bound organelles. Richly colored chloroplasts. Chain-like compartments.” She paused a beat, confused. “It’s green algae, Marty. So what?”

“Keep looking.”

“There are some brown-pigmented foreign body structures as well. Thick-walled, elongated cells, axially orientated.” She looked up at him. “Wood cells?”

“Indeed.”

She frowned in confusion. “I suppose I could understand a bit of algae growing on the stingray’s barb. But what’s wood tissue doing there?”

“It’s not just on that barb, Elsa. It’s on the base of all three.”

“Again, Marty—so what?”

“You told me you’ve followed my work,” he said, pacing eagerly. “You should know then that I hypothesized that merfolk are a tool-wielding species, likely on par with early hominins.”

Elsa now understood what had gotten him so animated. “You believe that these barbs were lashed onto sticks with some sort of aquatic plant? That they were the tips of…crude spears?”

“Spears or harpoons, yes. Is there any other explanation?”

Elsa kept her poker-face dutifully in place as she wondered how to proceed, how to make him see reason…and realizing in the process that such an effort would be futile. He was going to believe what he wanted to believe, what he had long ago programmed himself to believe.

She said, “There are countless other explanations, Marty.”

“Name one.”

“A lot of wood sinks to the ocean floor. It creates ecosystems for all kinds of fauna—including stingrays.”

“Since when do stingrays attack wood? And the wood tissue was on the base of the barbs, Elsa, not the tips. Both the wood and algae tissue, on the base. Why would that be? Why only on the base, which would have been sheathed in the ray’s tail before the barb broke off?”

“Marty…”

“Wood tissue on all three barbs, Elsa.”

“You’re making assumptions and leaping prematurely to conclusions.”

“I know, I know.” He ran a hand through his hair, fidgety, distracted. “I need to study the diagnostic anatomical characters of the wood and algae tissue to make exact identifications. I need to recreate a spear or harpoon with the identified material, test it under laboratory conditions, confirm it could be used as a viable weapon…”

“Marty…”

“Open your eyes, dammit!”

“My eyes are open!” she shot back. “As is my mind! But this is just”—a number of derisive adjectives crossed her mind before she blurted—“ridiculous.”

He fumed. “Ridiculous? Really?” He shook his head. “No, why do I bother? What does it matter to me what you believe? I couldn’t care less.”

“I’m glad I’m not alone in the Marty-doesn’t-care-what-you-think category.”

Elsa turned to see Jacqueline DeSilva and Radhika Fernandez standing at the rollup door. It was the TV host who’d spoken. She held a green smoothie in one hand. Her dog was poking its head out of her beach bag, panting in the heat.

Marty wasted no time explaining to them the discovery of the extraneous biological matter on the stingray barbs.

Radhika said, “Spears? Merfolk use spears?”

Jacqueline said, “My God, this story is going to be huge!”