As we noted in our breakdown of the details you might have missed in "Stranger Things" season four, the flashback to Eleven's attempted escape from Hawkins Lab shows her running down a familiar flight of stairs.
Hopper was in that same stairwell when he was grieving over his daughter's death in a hospital room. Does that mean Sara died inside HNL? This season we got the reveal that Hopper believes that Sara died due to birth defects related to Agent Orange. But why would that have landed her in the secret hospital lab in Hawkins?
Insider asked Harbour back in 2017 if he could tell us more about this connection between Sara's hospital room and the HNL.
"Hmmmm [laughing] I can not," Harbour said. "But yes, it is the same location. So that's interesting. Or it's a similar location. But there's actually another thing you'll notice which is that there's a stuffed animal lion that appears in Eleven's room when he breaks into the lab and finds that room, and it also appears in Castle Byers, and it also appears on Sara's lap."
For a full breakdown of all the connections between Hopper, his daughter Sara, and Eleven, read our full report here.