Complex sentence: Darcy notices a blood trail leading to a nearby closet--which, when opened, reveals the murdered body of the morgue attendant, confirming that Red John is still alive, either following Darcy or has access to her files.
Split into simpler sentences: Darcy notices a blood trail leading to a nearby closet--which, when opened, reveals the murdered body of the morgue attendant. This confirms that Red John is still following Darcy during her investigation or else has access to her files.