i and Shelton hurried along Beaufain Street. They the passed crew teams rowing on Colonial Lake, a man-made oval stretching a full city block. Ducks paddled in noisy clusters of two and three. Intent on their task, the boys barely noticed.

Near the shopping district, single-family homes gave way to townhouses arranged in orderly rows. Window boxes overflowed with petunias, marigolds, and lantana. Honeybees worked overtime in the warm afternoon sun. The beauty of the day was lost on them.

Hanging a left on King, Hi and Shelton finally reached the CU campus, three square blocks of Gothic stone and ivy rubbing shoulders with modern brick and glass. Beneath ancient oaks and magnolias, dogs chased Frisbees hurled by college kids.

A sign directed the boys to a massive stone building on the eastern edge of the common.

“Any blackouts today?” Shelton asked as they hurried along the path.

“Nope, but I had a flare. For few moments I could read the answer key on Mr. Hallmark’s desk. I was in the back row.”

“Mine was auditory,” Shelton said. “In the bathroom I heard a ripping noise, like a power saw. It was Kelvin Grace, unzipping his fly. Ten feet away, outside the stall. Crazy, huh?”

“Barking mad.”

In the bio-med library, the boys asked and were directed to the veterinary wing. There, they divided topics and set to work. Two hours later, they compared findings.

“I scoured a billion medical journals,” said Shelton. “No disease matches our symptoms. I couldn’t even find some of them.”

“Here’s what I got on parvo,” Hi said, shuffling papers. “They’re tiny buggers, some of the smallest viruses in nature, with only a single strand of DNA. Parvus means small in Latin.”

“Fascinating,” Shelton deadpanned. “How does that help?”

“Different species have different strains. Dogs, cats, pigs, even minks. And listen to this.” Hi read from his notes. “Parvoviruses are specific to the life forms they infect, but this is a somewhat flexible characteristic.’”

“What does that mean, flexible?” Shelton asked.

“It means the viruses aren’t completely species-specific. Canine parvo usually affects only dogs, wolves, and foxes. But certain strains can infect other animals, like cats.”

“So if the dog version can jump to cats, why not to people?”

Hi shrugged. “Beats me. But Tory was right. Canine parvovirus isn’t supposed to affect humans.”

“Then that’s a dead end.” Shelton sighed. “We’d better keep looking.”

Shadows deepened, lengthened, eventually shot like dark arrows across the wooden tables centered in the room. Shelton had almost given up when he stumbled upon a new lead.

“Hi. Look at this.”

Hi leaned over to read the page under Shelton’s pointing finger.

“Humans can’t be infected by canine parvo, but they can catch viruses from the same family.” Shelton sounded excited.

“Really?”

“There are three types: dependoviruses, bocaviruses, and erythroviruses. The last type has a bug called Parvovirus B19.”

“Parvo B19.” Hi rubbed his forehead. “Why does that ring a bell?”

“B19 was discovered in 1975.” Shelton continued picking out facts. “It was the first parvovirus proven to infect people. There’s still no vaccine. The last epidemic was in 1998.” Shelton looked up. “Kids get it, mostly. Outbreaks are usually in nurseries or schools.”

“What does B19 do?”

Shelton returned to the journal, again skimmed. “It leads to something known as ‘fifth disease’ or ‘slapped cheek syndrome.’” Shelton’s eyebrow rose. “Those names sound made up. Anyway, it looks like all B19 does is cause a bad rash for a few weeks.”

“That’s definitely not what happened to us.”

Shelton continued reading. “B19 spreads via infected respiratory droplets. Coughs, I guess. Infected individuals can experience fever and fatigue.”

“Now that sounds familiar.”

Shelton nodded. “Once inside a host, B19 invades the red blood cell factories in the bone marrow. Symptoms begin a few days after exposure and last a week. Those infected are only contagious before showing symptoms.”

“We caught our virus from Coop,” Hi said. “Can dogs get B19?”

Shelton scanned the page. “No. B19 only infects humans.”

“Then this is another dead end.”

“I don’t know. This seems important. We must be missing something.”

“Let’s copy the article then check out the references cited.”

The shadows faded to gray, then black as Shelton and Hi pulled every source they could find. Loops led to loops and more loops. Nothing else jumped out at them.

At ten o’clock, the intercom clicked on and a prim voice informed patrons that the library was closing.

“I think we’re onto something,” Hi said. “I’m just not sure what. Let’s bounce this off the others.”

“Good idea.”

A second warning was broadcast, somewhat chillier than the first.

The boys headed for the exit.