Leaving No Door Unopened

After a whole morning of lolling around and doing nothing, I decided to explore. 

"Right, where shall I start first?" I mumbled to myself as I walked softly around the corridor. 

To my right were 7 rooms in total, the 3rd being mine and the last of the seven being Sven's. Slowly, I turned the knob of the first room and pushed the door open, not surprised that dust was there to greet me. I kept in the irritated cough that was about to escape me and moved on to the next door. Same old: Dust, a bed, a nightstand and a rug greyed with dirt. I closed the door and walked past my room to the 4th one. Nothing special, everything coupled the other rooms.

Mama hadn't been lying when she said that all the rooms were the same.

A little bored now, I moved my hand from the 4th doorknob to the 5th one and was confounded that it didn't open when I gave it a twist. 

"What the heck..."