ENT:Extinction

While still on the search for the Xindi, the crew sends an away team to an uninhabited planet. Soon after landing, all of the party but T'Pol begin to change. While Phlox tries to discern the best way to deal with the issue, an alien ship and threatens to destroy the Enterprises infected crew members. The aliens are instructive however as the Enterprise crew learn that the planet's long gone inhabitants, the Louque'que, had become sterile and in a bid to avoid extinction, introduced a mutagenic virus into the planet's atmosphere that turned other humanoids into members of their race. Naturally they are able to retrieve their crew without any losses, while sending a cure along with the aliens.