Therefore, its known narrative elements are not a part of the Doctor Who universe as we, on this Wiki, choose to define it. It may have been the basis for a similar story in another medium, however — and that story may indeed be valid.
The basic idea was these bodysnatchers, aliens who could only inhabit the dead. The villains in his human corpse had got this fossilised remain of some sort of Silurian god and were planning to clone it. Towards the end the villain was to get more and more decrepit in each episode, until there was just a skeleton at the end. ...It was meant to be an Evil Dead-type of thing, but I would have toned it down for Doctor Who.