Mari arrives on Last Island, a place that feels like it’s at the end of the earth, ready to work and excited to be reunited with Anne, her mentor from graduate school and a highly respected molecular virologist. But Anne is in over her head, taking on a massive sample collection project on her own. Mari suggests she should bring a larger team to the island, but Anne is secretive and guards her work. She and Mari spend a day collecting blood samples and nasal swabs from the seals, hoping to find answers about the virus that’s tearing through the population. They begin to see signs of something much stranger at work: birds and seals with deformations, missing eyes, strange extra gills and flippers. It seems the virus is somehow causing genetic mutations. Mari tries to convince Anne to raise the alarm and get off the island so there’s no risk of infection, but Anne reveals that it’s already too late: she’s contracted the virus. She shows Mari a small set of gills growing on her neck. Horrified, Mari tries to leave the island, but begins to feel an itch on her neck… and realizes it’s too late for her, too.