This episode puts aside the workings of the lab an produces a really nice police drama. It allows the plot to supercede the science, depending on some great twists, bad bad guys, and the personalities and qualities of he regular cast. Catherine and DB go underground, using the resources of street people to assist them after Catherine is wounded. There is a scene with body bags that is reminiscent of The Count of Monte Cristo. There is also an emotional conclusion which, if you've been watching regularly, comes as no surprise.