The Three Doctors (Doctor Who) the Third Doctor (Jon Pertwee) for help when Omega drains their civilisation's power. The serial opened the tenth anniversary year of the series, and features the first three Doctors all appearing in the same serial. This makes it the first "Doctor Who" story in which an earlier incarnation of the Doctor returns to the show. A superluminal signal is sent to Earth, carrying with it an energy blob that seems intent on capturing the Doctor. The homeworld of the Time Lords is also under siege, their power being drained through a black hole. Trapped themselves, and desperate to send help,
The Master (Doctor Who) stopped by the Doctor. The Master has featured in spin-offs of the series, which are of unclear canonicity and may not take place in the same continuity. The Master in these stories is, nevertheless, recognisably the same character. One of the most notable of these other appearances is David A. McIntee's "Master trilogy" of novels comprising "The Dark Path" and "First Frontier" in the Virgin Publishing lines and "The Face of the Enemy" for BBC Books, and the "Doctor Who" radio dramas produced by Big Finish Productions, in which Geoffrey Beevers has reprised the role, with a new incarnation being