"The crew of the other Enterprise haven't launched an invasion," said McCoy as he worked, "they've launched an infection. They're a disease vector. Think of the portal as an open wound and their ship as a syringe full of infected cells they've injected into the body of our ship, sending forth diseased cells to corrupt the healthy cells - that would be the crew - of our Enterprise. Judging by the speed with which the infection has spread on Halka, its sheer virulence, if you had allowed even one of them to break through into the general population of the ship, we could have lost the Enterprise."
"That bad?" said Kirk, rubbing his chin.
"That bad, Jim," said McCoy. "If the situation had reached that point you'd have had no choice but to destroy the Enterprise, hopefully taking the other one with it. Whatever happens, we daren't let this thing gain a foothold in our universe."
"Do we know anything about the cause of the infection?"
The Captain, Spock and I were watching Dr McCoy dissecting the zombie with Nurse Chapel assisting him. We needed answers, and we needed them fast.
"Toxoplasma gondii!" said Dr McCoy, looking up from the corpse he was autopsying and snapping his fingers, the desired effect of this action thwarted by the rubber gloves he was wearing.
"Is that the disease causing this?" asked Kirk.
"What? Of course not!" said McCoy, looking at us as if we were idiots.
"Then why mention it?" said Kirk, sounding exasperated.
"I believe I understand what has the Doctor excited," said Spock. "The parasite Toxoplasma gondii is a protozoa that used to live in most warm-blooded animals on Earth and was heavily implicated in schizophrenia in humans. It prefered home was cats, where it reproduced. To return to its feline host, it manipulated the behavior of mice and other animals it infected, making them lose their fear of cats, who then ate them. This returned the parasite to a cat's body and so ensured the completion of its lifecycle."
"You think something similar is happening here?"
"It makes sense," said McCoy. "For organisms that lack any intelligence, parasites can sometimes exert remarkable influence on the behaviour of their hosts. The crew of that other Enterprise are all still as intelligent as ever they were, but that intelligence is being bent to a single purpose: spreading the infection."
"So the grey skin, the weird eyes, and the resistance to phaser stuns..." I said.
"All just the effect the parasite has on the host body. I'd theorize that the resistance to phaser stuns is due to some sort of super-charging of the nervous system, enabling it to withstand blasts that would paralyse someone not infected. I'll know more when I've studied the samples I'm taking from all this man's major organs."
"Will you be able to come up with a cure, something we can weaponize to use against the zombies?"
I smiled at this. Without noticing he was doing so, Kirk had also started calling them zombies.
"I doubt it. In the case of Toxoplasma gondii, once the parasite became deeply ensconced in brain cells, getting it out of the body proved impossible. It formed thick-walled cysts around itself that were impregnable to antibiotics. This thing, whatever it is, looks like Toxoplasma gondii on steroids and probably has defences to match."
"Well, keep at it, Bones. In the meantime, we need to get back to the bridge."
"When the other Captain Kirk lifted their image manipulation he also stopped blocking our scans," said Spock. "I suspect he did this for the psychological effect that seeing the charnel house his ship really is would have on humans. His doing so enabled me to download files from his ship's computers. With your permission, Captain, I would like to devote myself to the study of those files. If we are fortunate, they may contain something that will aid us."
"Good idea, Spock. Report to me with any findings."
Spock departed for his quarters, which left me and Kirk riding the turbolift up to the bridge together.
"I think I may have a way of disrupting their beam," I said. "What if we use a shuttlecraft?"
"If a shuttlecraft got in the path of those beams it would be destroyed," he said.
"Which is why I'm not proposing getting it in the path of the beams. What I had in mind was using it to damage their deflector dish by ramming it."
"That could work," he replied, looking thoughtful. "Scotty should be able to tell us where to aim for to cause maximum damage. But it would be a one-way mission. As soon as their deflector is damaged and the beam disrupted the portal will collapse, leaving whoever pilots it trapped in that other universe."
"Not necessarily," I replied. "I have a plan..."
