1x5: Chapter Five: The Flea and the Acrobat
The boys are interested in Mr. Clarkes information about interdimensional travels. In the meantime, Nancy and Jon face Will and the entity that possessed him.
This episode's title refers to the explication brought by the school's teacher about alternate dimensions: "The Flea and the Acrobat".
Hopper's investigation ends up in the Hawkins National Laboratory, so he must sneak in if he wants to find some real answers. He finds himself by the portal to the Upside Down. After being discovered Hopper wakes up in his house, full of drugs and alcohol, and searches for any installed microphones that could be used to spy him. The relation between Joyce and Hopper finds a new development.
As Mr. Clarke said in the past, the portal has a electromagnetic power that makes all the compass fail (this same things happens in the movie Event Horizon). On the other hand, Steve asks Nancy to go the cinema to watch All the Right Moves. Finally, the scene with the vertical cell reminds us of Star Wars: The Empire Strickes Back