The cast of Netflix's 'Stranger Things' season 4 opens up to ET's Will Marfuggi about their character's more mature story lines, as well as the impending danger this season. Joe Keery and Natalia Dyer talk about Steve and Nancy's romantic tension, while Sadie Sink discusses Max's trip to the Upside Down and how Kate Bush saves her life. The first seven episodes of 'Stranger Things' season 4 are now streaming on Netflix.