It looks like you're asking for a story summary or recap for Snowpiercer Season 1, Episode 3, specifically the version (which just indicates the video quality/source).
Meanwhile, (now revealed to the audience as the true, secret ruler of the train) is growing desperate. The train’s eternal engine is failing. She needs an engineer. She secretly grooms Jinju (a high-ranking First Class worker) to replace the aging, alcoholic Engineer Miles’s grandfather, while also keeping the fiction of "Mr. Wilford" alive. snowpiercer s01e03 720p web-dl
Layton has been promoted to Detective —a title with no real power. He is given a small closet to sleep in near Third Class, a token uniform, and a permanent escort, Osweiller (a brutal, loyal "Brakeman"). Layton isn't solving the murder of Sean (the tailor) to find justice; he's a pawn in a larger game. It looks like you're asking for a story
Layton corners a suspect: a Brakeman named LJ’s father (the father of the creepy, fanatical First Class girl, LJ Folger). Before he can get answers, Osweiller arrives not to help, but to silence. Osweiller slits the suspect’s throat in front of Layton, then calmly says: "Your investigation is over. The killer killed himself." She needs an engineer