What is "shada"

Shada is an unaired serial of the British science fiction television series Doctor Who. It was intended to be the final serial of the 1979–80 season ( season 17), but was never completed due to strike action at the BBC during filming. In 1992, its recorded footage was released on video using linking narration by Tom Baker, who played the Doctor in the serial, to complete the story.

The script, with adaptations, was later produced by Big Finish Productions as an audio play, with animation and was made available on BBCi and the BBC website in 2003. This version saw Paul McGann take on the role of the Doctor, with Lalla Ward reprising her role as Romana, with an otherwise different cast.

A novelisation of the story written by Gareth Roberts, returning the action to the Fourth Doctor and Romana, was released in March 2012.