Contains spoilers for this episode and earlier episodes.
A mining company hires Lightman to challenge a safety report after an explosion kills six men. The company wants the deaths blamed on human error, but interviews with survivors reveal anger and concealment around foreman Johnson. Cal and Loker question the crew at their bar, where hostility turns physical. Johnson was locked inside a room as a prank, and his attempt to escape created the spark that ignited dangerous methane.
The prank does not explain why the gas reached that level. Johnson had switched off ventilation to save money under pressure from executive Wallace. Cal goes underground with the miners and recreates the danger to force them to explain their actions. Above ground, Loker protects Connie after a crew member threatens her because she knows too much. The confrontation ends with Connie holding a gun on Wallace, who agrees that the company will accept responsibility and pay damages.
Gillian and Torres meanwhile deal with Dillon's demand for help catching criminals from a poker game involving Cal. The investigation reveals that Cal joined the game to help a man trapped by gambling debts. Gillian trades the location of another game for an agreement that Dillon will leave the consultancy alone. Afterwards, she and Torres celebrate with Cal's expensive whisky. Cal returns from the mine and acknowledges Loker's work, then finally thanks Gillian for resolving the FBI pressure.