The people at the Investigation Bureau had good reason to use it to test the strength of Spiritual Perception.
It gave a sense of infinity, layer upon layer. Only people with sufficiently strong Spiritual Perception could see more doors; otherwise, they would see only two layers of doors.
Standing before the Infinite Door, Ke Meng could sense something behind the hole where the doorknob had been.
By now, the people at the Investigation Bureau had given up on testing the Infinite Door. It wasted both electricity and manpower.
"Well? Can you sense anything?"
"Have the doors inside been closed?" Ke Meng asked.
"We opened too many doors. So far, we've only closed the first fifty. All the doors beyond those are still open," Director Zhang replied.
The bureau had opened the door far too many times while testing the Infinite Door. Closing them meant repeating the whole process, which was too much trouble, so they had left the doors farther in open.
Ke Meng leaned toward the doorknob hole and pointed his phone's camera through it. He turned on the flash to illuminate the interior, then checked the screen. Sure enough, he saw a red wooden door.
But once he moved the phone's camera a few centimeters away from the hole, it could no longer capture the scene beyond. All it showed was pitch-black darkness.
Ke Meng had yet to push the door open. He put his phone away and looked through the hole with his own eyes.
With his eye still ten centimeters from the hole, he saw only darkness, though he could vaguely make out the illusion of a red door.
When he pressed his eye to the hole, he could clearly see the next door standing closed inside.
Why keep it closed? To make Spiritual Perception testing