A sequel (but in terms of time frame a prequel) to the Fourth Doctor television story Terror of the Zygons.

It isn't very well written, and it is strangely unengaging at the best of times. The introduction of the Zygon sting which was edited out of the television story.

The story meanders around and wraps itself up but the payoff is dim and the lack of any real point to any of it, not to mention the monstrous (pun intended) incongruity of the set piece, leaves it as a bit of a wreck.