(Season Four episode list here
The episodes "Afflicton"
reveal the origin of the smooth-headed Klingons seen in TOS. The Roddenberrians could have simply pretended that the Klingons had the cranial ridges all along, they way they pretend that Andorian antennae always protruded from the forehead, but the DS9 episode "Trials and Tribble-ations"
committed the Star Trek
canon to the change in Klingon appearance.
Our adventure begins when aliens kidnap Phlox and deliver him to a Klingon research facility, where he is pressed into finding a cure for an illness that threatens millions of Klingon lives. He traces the illness to a mutated flu virus, and recognizes traces of human Augment DNA. The Klingons had recovered some of the embryos from the wreckage of the ship captured by Augments earlier in the season, and used them to conduct their own Augment research. One of the rersearch subjects had the flu, and the Augment treatment turned the flu into a lethal plague.
Back at Earth, T'Pol performs a mind meld on Sato, who was with Phlox at the time of the attack. Sato recalls that the captors spoke Rigelian. Enterprise
tracks down the ship that took off with Phlox but finds it destroyed; no trace of Denobulan DNA is present. A Klingon vessel attacks and beams aboard several Klingon Augments who sabotage the warp matrix. During a firefight all escape by transporter, except for one who is stunned by a phase pistol. The crew is confused when it discovers that the human-appearing saboteur is Klingon.
They also learn that the black box
recovered from the Rigelian ship was erased. Investigation traces the act to Reed. Archer has him thrown in the brig, and unsuccessfully tries to pry his tactical officer for information. Reed withholds (for now) the fact that he is working for the Section 31
. Reed had been in subspace contact with Harris, his control at Section 31, but had erased his communications logs. T'Pol is able to reconstruct a portion that turns up Harris' name.
The sabotage threatens to blow the injectors, but this can be alleviated by maintaining high warp. (Sound familiar
comes to the rescue. In a great visual, the two ships fly within 50 meters of each other, and Tucker travels along a tether to get to his old ship to perform an emergency cold start to the warp engines. (Inconsistency alert: in the TOS episode "The Naked Time"
Kirk says that such a cold start had never been done before.) He saves the day, and the two ships proceed into Klingon space to rescue Phlox.
Archer learns from Reed of the existence of a medical research facility where Phlox is likely being held, and from the Klingon prisoner (with some effort) the facility's location.
At the facility, General K'Vagh orders Phlox to perfect the Augment process; Phlox refuses, wishing on no one a repeat of the Eugenics Wars. He and the lead Klingon physician Antaak (played by an engaging John Schuck) trick K'Vagh, pretending to comply with his order while actually seeking a cure for the plague. Enterprise
arrives, and Archer beams down. Phlox has a cure, but needs a host to produce antibodies. Under duress, he agrees to allow the captain to fill that role.
But there's a deadline to meet. The Klingon authorities had decided to contain the plague by sending Fleet Admiral Krell to destroy the research installation. As Enterprise
battle the Klingons as the base is bombarded, Phlox comes up with a plan that his evil twin in the mirror universe
might admire. He beams a container of the contagion over to Krell's ship, infecting the entire crew, giving Krell a powerful incentive not to destroy the base that houses its cure. The sterilization program is cancelled, Reed gets back into Archer's graces as he severs ties with Section 31, and Antaak ponders a career in cranial plastic surgery.
This two-parter answers one question and raises others. Note that the softening of the cranial ridges was a result not of the Augment treatments but of the mutated virus. So, instead of two sets of Klingons you've got three: the original stock, non-Augments like Antaak and Krell who contracted the virus, and Augments, all of whom were also infected. What kind of jolt to Klingon history does this bring? It wouldn't be surprising if the two sets of infected Klingons were branded with some sort of dishonor (or worse), and this event would eventually trigger a civil war that the smooth-heads would win, explaining their predominance in the TOS-era Klingon fleet. It also wouldn't surprise me if Krell were to seek revenge against the Denobulan who intentionally infected him and his crew
. I smell some movie plots.