I'm looking for a story that starts with some mad scientist releasing a chemical (sexpollen) into the water supply (?), and all citizens in DC are infected und pair off (like finding their true love). So do Mulder and Krycek, who just happen to run into each other. Later, Mulder reports to Skinner, who tells him that agents are now categorized, depending on who they slept with (normal citizens, minor criminals, dangerous criminals). Also the pairs get real angry and violent if their partners are threatened.