- You may be looking for the Class audio story.
An unnamed story was to have been the third of four The Sarah Jane Adventures Halloween specials proposed to be aired in 2011. However, due to the death of Elisabeth Sladen, it was never produced.
It would have seen Sarah Jane and her gang encounter a Gargoyle-like creature.
It would have been succeeded by the last Halloween special, Phil Ford's Night of the Spectre. (REF: DWMSE 32)