When an arm bounces from underneath a bus, the CSI team is called to determine what happened. They discover the remains of a body beneath the bus. Considering that the bus was carrying inmates from a women's correctional facility, it's perhaps not surprising that someone might try to escape -- but when it's discovered that the person was dead *before* the trip began, the case takes an interesting turn. Meanwhile, Grissom investigates a man stabbed once in the front and four times in the back -- all wounds at exactly the same height.