An engineering catastrophe on Snowpiercer forces Layton to make a difficult choice, one that might cost him everything.

Melanie embarks on her most dangerous mission yet, while Layton reckons with his personal choices.

Dr. Melendez, Dr. Brown and Dr. Park have given a young married couple two choices about their future: save the wife’s life or their future ability to start a family….

Sam and Castiel follow up on a lead about the Mark of Cain. Dean and Rowena meet.