A creature lurks inside a sinister government research facility in episode 1x01 "Chapter One: The Vanishing of Will Beyers". Eleven remembers being put into solitary in episode 1x02 "Chapter Two: The Weirdo on Maple Street". Chief Hopper leads a brief police search of the lab for signs of Will in episode 1x03 "Chapter Three: Holly, Jolly". Appears in 13 more episodes.
Dorothy goes over to the other computing building to deliver some documents to Vivian Mitchell and to ask about the new construction in the tech wing. Later, Vivian goes up to Mary during lunch to tell her she doesn't meet the requirements for the training program.