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).
Layton stares in horror. The message is clear: the train’s power structure will never allow a Tailie to expose their secrets. snowpiercer s01e03 720p web-dl
The episode’s title becomes clear: physical access cards are the only currency that matters. Layton discovers that Sean’s murder wasn't random. Sean was a "Jackknife"—a smuggler who helped people move between classes. He had been stealing access keys to the mysterious "Drawers" (a hidden cryo-section of the train). It looks like you're asking for a story