Behind the Metal Door

There was only one rule: don’t open the door. That’s what Sara Mitchell said.
Josh looked at it with curiosity.
“Ok Miss Marchell.”
Saras son looked up at Josh as his mother walked out the door. “Wanna play basketball on the Xbox?”
“You ready to get beat?” Steve, his babysitter said
“Yeah right! I’ll kick your butt.”
Josh looked at the closed door again, it was metal, it looked heavy. He wondered what was behind it. A secret lab? A server room and Miss Marchell was actually a secret agent? He shrugged it off and got back to the game.
A few hours later, “Go brush your teeth and get into bed bud.” Josh said
Steve yawned and walked to the bathroom.
A few minutes later he came out, said goodnight, went into his room and hopped into bed.
Steve sat on the couch and looked for a movie to watch but that door was still on his curious mind. He walked up to the door and looked at it for a bit “Nope, don’t open it.” The door was locked but his father was a locksmith and taught him how to pick a lock at the age of 10.
“What would it hurt to take a little look; she’d never know.” He got out his lockpick set, it took him a while to pick it but he did. He had to push the door with a lot of strength to open it. He looked inside but it was empty.
“Is there some invisible technology in here?” He walked in and all of a sudden, his head started hurting, a few seconds later he walked out the door and closed it with an evil laugh and smile.