Molly and JD discover another pregnant woman suffering from inexplicable and fatal symptoms, while Molly begins to question her own mental stability. Meanwhile, Julie struggles with Ethan's rebellion.

As Molly works to create a virus that will eradicate alien hybrids, she discovers that aliens are trying to communicate with humans through a hidden message in their DNA. Also, Lucy helps Ethan run away from Charlie in order to help him recover memories of his mother, Molly.