Chekhov's Law, also called "Chekhov's gun", is a creative technique first elaborated by the famous Russian short story writer Chekhov. It means that every element mentioned in a story should be mentioned later, otherwise there is no need to mention it. According to this concept of "causality" and other theoretical logic, we construct a story with reverse time memory as the main setting and non-linear narrative as the starting point. The story is set in the case of a reverse-time sensing virus called TDV that has a parasitic relationship with the blue-blooded limulus crab. Humans were exposed to the virus while fishing for horseshoe crabs, and TDV eventually began to spread among humans. People infected with the TDV virus begin to experience reverse temporal memory symptoms and eventually have only seven days to live. Researchers A and B at the EMRD Institute were also infected by TDV virus due to their participation in secret research and experiments related to limulus in the institute. The two of them worked together in the last seven days to research and collate the data related to the TDV virus, and eventually died one after another. Since they were well-known in their respective fields, their deaths also caused a considerable stir in society. In combination with this story and the inspiration source of the story structure of "Chekhov's Gun", we take drama as A part of the form of expression, and arrange several scenes in which A and B were active before their death in a separate act, and combine realistic scenes with real composite images to produce the reasoning process of the story. The player will play as an investigator who comes to investigate the cause of their death, and go to these scenes we have arranged, by analyzing the evidence left behind by the AB who is in the same space but different time, to achieve a dialogue across time and space, and explore the truth leading to this backward time memory event. The cogs of fate had begun to turn, and as Chekhov said, the gun that hung on the wall in the first act was bound to fire in the third act. In the scenario we set up, the audience watches and collects layers of evidence by following the guidance, and finally the "gun" in their hands may be the key to solving the mystery; Autopsy reports that appear out of nowhere, a strange experimental study of the pineal gland, a blue-blooded creature that supposedly lives in the deep sea but turns up in the lab... Only when the game is finally broken can the audience understand the meaning of their existence. In our story, it is the death of the scholar that reveals the virus that allows the audience to participate in the story as an investigator; Even if the two scholars get the ability to predict the future, they will eventually die because they have been involved in this secret research; And the new unknown virus caused by human wanton demand and killing of natural creatures has gradually begun to spread in the population in a way that has never been done before. The result is that the "gun" we cast will eventually run through our eyes.