There are too many unsolved mysteries in this world, and some seemingly solved mysteries still contain hidden secrets.

Here, there is an example.

It happened five years ago.

The location of the incident is a small town in the middle of the United States.

The town was built around a university. There are less than 10,000 original residents in the city, but the university has recruited a total of 30,000 teachers, students and staff from all over the world.

The outskirts of the town are dotted with large tracts of farmland. On a clear day, slender clouds hover between the sky and the fields, and are dotted with scattered red barns, outlining the empty and transparent scene.

The city is peaceful and peaceful, but it is also full of life.

The liveliest place is the central square of the university. Two intersecting walkways divide the expansive lawn so that students who are rushing to class and resting on their backs have their own space.

On the morning of the incident, a group of cheerleaders were practicing stacking arhats on the grass. A few boys with smirks on their faces lay on the sidelines, pretending to look up at the sky. On the sidewalk, a student on a bicycle knocks a professor's coffee cup to the ground. A skateboarder whistled past the two and whistled loudly.

At this moment, a man dressed in a maintenance man's costume carried a female college student covered in blood to the intersection of the sidewalk in full view. He laid the girl flat on the ground, poured gasoline on her, and polished a match......

The following is a specific description of the incident.

The scorched girl's name was Cecil. The name of the repairman who committed the murder was Donald. He has a wife, Kelly, who teaches dance classes at college.

To the north of the central plaza is a building that spreads out east-west and is the same width as the plaza. There is a side door with cameras on each side of the building.

The building was redesigned a few months ago. Its interior is separated by hollow walls and divided into two separate areas, the school building on the west side, where Kelly teaches, and the residence hall on the east side, where Donald works as a maintenance worker.

After the planning was completed, the main gate at the front of the building, facing the square, was no longer in use, leaving the two side doors as the only entrances and exits.

The only parking lot in the entire area is located outside the building's east gate. A narrow road extends from the south side of the parking lot, semi-encircling the central plaza and terminating on the west side of the building, creating a cul-de-sac. For the safety of students, there are no other roadways around the central plaza other than this path.

At 8 a.m., cameras at the building's east gate caught Cecil walking into the dormitory. At the same time, the west camera captured Kelly walking into the school building.

At 8:05, Donald walked into the dormitory building in the camera on the east side. Of course, during this time, the cameras also captured other students entering and exiting the building. The three were unobtrusive and did not make any strange moves.

For the next hour, Kelly took dance lessons. This can be attested to by more than a dozen Kelly's students.

At 9:15, Kelly leaves the school building and walks east in the west side camera. Half a minute later, the east camera caught her entering the parking lot.

At 10:19, a fire alarm sounded in the dormitory.

At 10:28, Donald walked out of the dormitory building with Cecil, covered in blood, carrying a bucket of gasoline and a toolbox.

Students who were driven outside the building by the sound of the alarm said that several loud noises could be heard from the break room on the first floor of the dormitory building before Donald showed up. Although no one saw what was happening, the police investigated and found that Cecil's blood was running down a table, and sporadic blood spots stretched from the floor of the break room to the door of the dormitory.

At ten thirty a.m., Cecil's motionless body began to burn.

At 10:33, firefighters arrived. Donald had disappeared into the crowd.

It doesn't end there.

At noon, the police came to Donald's home. A panicked Kelly claimed that she saw her husband returning home around eleven o'clock, but half an hour later she suddenly found Donald inexplicably hanging himself from the bedroom door. She wanted to put her husband down, but had to look for scissors because the rope was too tight, and when she returned to the bedroom again, her husband's body was gone.

In the evening, when the rain was at its highest in the night sky, a group of oddly behaved guys appeared outside Donald's house.

The mouths of this group kept repeating a puzzling word—spirit.