Spoilers for Stranger Things season 2 episode 3.
Dustin secretly brings the creature from his rubbish bin into his bedroom, feeds it chocolate and names it D'Artagnan, or Dart. He takes it to school, hoping that he has discovered a new species. Will recognises its noises from the Upside Down and remembers the creature he coughed up after returning home. Mike stops Dustin from presenting Dart to Mr. Clarke and argues that they need Hopper's help. Dustin resists, believing that Dart trusts him. When the creature grows legs and escapes, everyone searches the school. Dustin eventually finds it and hides it under his hat, keeping its location from his friends.
Hopper connects the dying vegetation to Hawkins Lab and demands an explanation from Owens. Joyce watches Will's Halloween recording and traces a shape in the picture that matches his drawing of the shadow creature. Nancy begins a plan to expose what happened to Barb, arranging a meeting with Mrs. Holland over a telephone line the laboratory monitors. Eleven leaves the cabin to find Mike but sees him talking with Max at school. She knocks Max from her skateboard with her powers, then disappears before Mike can find her. Outside, Will slips into another vision. Remembering Bob's advice about confronting nightmares, he stops running and orders the shadow creature away. It surges towards him and forces its dark substance into his body.