Robert returns to work, but begins to crack under the pressure. Christine deals with a young girl who has been hit by a bus, but denies the police access to the bus driver until she can determine the identity of a mystery substance found in the girl's bloodstream. Mike angers a young mother after accusing her of abusing her six-year-old daughter. A young girl with slash wounds to her wrists is found collapsed in reception, and Stuart takes a leap into the unknown by treating a trauma patient at the scene of a hit-and-run.