The 'Timekeeper' at 3 AM

In an antique shop at the end of an old street alley, sat an unnamed wooden clock. The clock face had no hands, and its internal gears had long since rusted and seized. Years ago, the greedy owner, Old Zhang, to take over the shop, locked his severely ill and paralyzed old partner in the back room late one night, faked an accidental death, and swallowed all the family fortune. Before he died, the old partner, like a madman, dug his fingers into the wooden casing of the clock, leaving five bloody marks. Ever since then, Old Zhang often woke up startled from nightmares. One night at 3 AM, the antique clock, long since broken, suddenly let out a heavy and monotonous 'Dong—Dong—' sound in the silent shop, ringing exactly three times. Old Zhang broke out in a cold sweat. He summoned a craftsman overnight to dismantle all the gears inside the clock, and even used chains to lock the clock door shut. However, the next night at 3 AM, the clear chiming sound rang out punctually again. Old Zhang, like a madman, smashed open the lock, only to find the inside of the clock empty, with only a few mottled strands of hair hanging on the wooden mallet. The third night, the bell chimed again. Old Zhang could no longer bear the pressure. Terrified, he rushed into the back room to pack his belongings and flee. The moment he stepped into the back room, the heavy wooden door suddenly slammed shut from the outside, locking itself in the iron frame. No matter how hard he pounded and cried for help, outside the door, only the antique clock continued to chime, one after another, at 3 AM. When the police arrived the next day, the back room door was intact. Old Zhang was found curled up in a corner, long dead. His hands were clenched tightly against the wall, his fingernails completely broken, leaving five deep bloody marks.