“Observer Effect” is episode eleven of season four of Star Trek: Enterprise.
Reid and Travis are playing chess in the mess hall. Their conversation seems a little off, which is confirmed when they talk about the possible outcomes of chess games and how humans only live about 100 years and have no time to play every possible game. NotReid tells NotTravis that they observe with no emotional involvement. They’re here to see how humans react to what’s on the planet; NotReid doesn’t expect humans to react differently to any other physical species. Yes, it’s possible their hosts might die today. Some species lose the whole crew, others only a few. But someone always dies.
Trip and Hoshi, both dirty from digging around in Klingon garbage, are heading back in a shuttlepod when Trip starts coughing before collapsing, forcing Hoshi to take over. Captain Archer and Phlox head to decon; the other landing parties returned with no ill effects. Phlox needs blood samples. Hoshi starts coughing and, when Phlox asks if there are any other symptoms, goes to throw up. As the captain and Phlox leaves, the doctor says whatever is affecting the two isn’t showing up on standard scans. No, that’s not good.
NotTravis and NotReid are discussing it. NotReid says this is typical of species at humans’ level of development, though NotTravis points out the Klingon captain blew up his shuttle. NotReid thinks this isn’t different; the launch bay and decon are isolated. They have nothing more to learn from humans. NotTravis says they are showing concern like Cardassians. NotReid points out that the Cardassians still killed their infected crew; it just took them longer. In 80-0 years of observations, NotReid has yet to be surprised. They still have to follow protocol. Which involves NotTravis going to decon and questioning Hoshi and Trip until Trip shuts the hatch and NotReid going to sickbay and questioning Phlox until the doctor kicks him out.
Phlox tells the captain that the virus is silicon based and highly contagious. Even though on a Class M planet all life should be carbon based. It may have been brought by a meteorite. There’s nothing like it in the Denobulan database and Trip and Hoshi have less than 5 hours to live.
NotReid says the pathogen is identified 37% of the time. And, as nothing has been done to get rid of the infected crew, this is likely one of the times everyone times.
The captain heads to see Hoshi and Trip and fills them in. Trip knows the human immune system can’t fight a silicon-based disease.
NotTravis is suggesting to NotReid that they inhabit Phlox and T’Pol to get a better view of events. NotReid is eventually talked into it. They spy on Hoshi and Trip, as Phlox and T’Pol, which was creepy. Afterwards, NotPhlox, the alien who was inhabiting Travis, thinks humans are brave. The other doesn’t think they’re advanced enough for first contact.
The captain wants to contact the Klingons to see if they developed a cure. The results Phlox was waiting for have come in, so the aliens decide to leave Phlox and T’Pol to their work and return to Reid and Travis.
Hoshi is becoming delirious and it turns out she’s capable of waltzing through security systems. Not something you want in someone with a highly infectious and deadly disease. The two aliens could help, but policy states they can’t. Though the alien who was originally inhabiting Travis would seem to like to. Reid’s inhabitant is far more dismissive. But if they don’t help and Phlox can’t cure the illness, Trip and Hoshi are dead.