Night of the Spectre was to have been the final of four Halloween specials but due to the death of Elizabeth Sladen was never produced. Unlike the other Halloween specials that were to be live broadcasts, Night of the Spectre was to be animated.
It would have seen the return of Alan and Maria Jackson, who last appeared in The Mark of the Berserker. Also, Sarah Jane and her gang would have encountered an enemy called the Spectre.
As this was the last of the Halloween specials it would have been succeeded by a sixth series. (DWMSE 32)