"Isn't there someone from Cabo Blanco?" Bowman asked. "That's where she was bitten."

"Unfortunately not," Dr. Cruz said. "Cabo Blanco has no permanent staff, and no researcher has worked there for some time. You were probably the first people to walk on that beach in several months. But I am sure you will find Dr. Guitierrez to be knowledgeable."

Dr. Guitierrez turned out to be a bearded man wearing khaki shorts and shirt. The surprise was that he was American. He was introduced to the Bowmans, saying in a soft Southern accent, "Mr. and Mrs. Bowman, how you doing, nice to meet you," and then explaining that he was a field biologist from Yale who had worked in Costa Rica for the last five years. Marty Guitierrez examined Tina thoroughly, lifting her arm gently, peering closely at each of the bites with a penlight, then measuring them with a small pocket ruler. After a while, Guitierrez stepped away, nodding to himself as if he had understood something. He then inspected the Polaroids, and asked several questions about the saliva, which Cruz told him was still being tested in the lab.

Finally he turned to Mike Bowman and his wife, waiting tensely. "I think Tina's going to be fine. I just want to be clear about a few details," he said, making notes in a precise band. "Your daughter says she was bitten by a green lizard, approximately one foot high, which walked upright onto the beach from the mangrove swamp?"

"That's right, yes."

"And the lizard made some kind of a vocalization?"

"Tina said it chirped, or squeaked."

"Like a mouse, would you say?"

"Yes."

"Well, then," Dr. Guitierrez said, "I know this lizard." He explained that, of the six thousand species of lizards in the world, no more than a dozen species walked upright. Of those species, only four were found in Latin America. And judging by the coloration, the lizard could be only one of the four. "I am sure this lizard was a Basiliscus amoratus, a striped basilisk lizard, found here in Costa Rica and also in Honduras. Standing on their hind legs, they are sometimes as tall as a foot."