A superluminal signal is sent to Earth, carrying with it an energy blob that seems intent on capturing the Doctor, but has already mysteriously abducted two individuals; a local game warden, and scientific researcher Dr. Tyler.

The Second Doctor later allows the TARDIS with himself, the Brigadier, and Benton inside, to be taken by the blob, although this causes UNIT HQ to be stolen as well.

Jo, the Third Doctor, and Dr. Tyler, whom they discover there, assess their situation in this new mystery universe of antimatter, inside the black hole.

Omega seeks revenge on the Time Lords, whom he assumes left him stranded alone for centuries in his universe, of which he explains that he willed into existence.

The script was originally supposed to feature all three Doctors equally, but William Hartnell was too ill to be able to play the full role as envisioned.

He was, therefore, reduced to a pre-recorded cameo role, appearing only on the TARDIS's scanner and the space-time viewer of the Time Lords.

One session of these took place in October 1972 at a photo studio in Battersea - this produced the image that was used for the cover of the Radio Times magazine to promote the story.

The same DVD commentary and the on-screen production captions note that the unavailability of actor Richard Franklin led to a shifting of the roles by the UNIT supporting cast.

Club reviewer Christopher Bahn summarised that the serial "has some good ideas in it, but they're treated with such an unambitious lack of imagination that there's not enough actually happening here for the story to be offensively bad—just boring".

He felt the "most enjoyable part" was the "comic squabbling" between Pertwee and Troughton, and also called the Brigadier a "saving grace".

[6] DVD Talk's Ian Jane gave the serial three out of five stars, noting that it was "slightly silly" and the production designs and special effects were "definitely not the best that the series has had to offer".

The Three Doctors was released twice on VHS, first in August 1991 and thereafter remastered and re-released in 2002 as part of the WHSmith's The Time Lord Collection boxed set.

Some copies came in a box set housing a limited edition Corgi model of "Bessie", the Third Doctor's vintage roadster.

A special edition of the episode aired on BBC iPlayer on 1 November 2023, in the spin-off Tales of the TARDIS.