This story is a sequel to Hard Reset

After the events of Hard Reset Twilight's life and mental well being are slowly returning to normal. Her recovery is cut short, though, when a letter arrives informing her that the time loop spell she cast is causing severe damage to space and time itself. In over her head, Twilight tries to summon anypony who will know how to fix it. The pony she gets is the last one she ever thought she would meet... and nothing like she expected him to be.

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Series TV Tropes page

Ponyville is shaken to its core when a body is discovered in the Everfree Forest. As the townsponies grieve, the mysterious Special Agent Bentgrass from Their Majesties' Royal Investigative Service arrives at the Books and Branches library and drags Twilight into a world she's only read about: lies, corruption, suspicion, and murder.

Faced with an indifferent police force, and Agent Bentgrass's infuriating methods, Twilight must put the pieces together and catch the killer. But as blood continues to spill and questions pile up, one thing is terrifyingly clear: in the dark of the Everfree, much more is at play than mere murder.