The only problem is that the show has already run into problems with showing things that have deemed too scary for younger viewers, and so this is a horror story that's had all the terror taken out of it. It's about as spooky as a dirty tea cup, and whether it's by accident or by design, the cast seem much more invested in the fun aspects of these episodes than the scary ones. Witness, for example, the (admittedly rather wonderful) discussion between the Doctor and Leonard de Vries of the three missing paintings, where they regard each blank space where a painting used to be in turn, talking about the subjects that were portrayed in each. Tom Baker and Nicholas McArdle seem far more engaged in this scene than in the one where de Vries is preparing to sacrifice the Doctor to the Cailleach, which feels like it's being played more for laughs than with any serious intent (at least from Tom Baker's point-of-view). And even the idea of the Cailleach posing as the Doctor in order to try and kill Romana has been softened to avoid upsetting viewers -- so now we just get an off-screen voice and Romana telling us about it afterwards (once she's decided to trust the Doctor again).
All that said, there are some good moments here. The use of the crows is really good, and the screen lights up any time Beatrix Lehmann is on it as Professor Amelia Rumford -- while Susan Engel also does a good job as Vivien Fay and is a good choice as the true villain of the piece (even if those three separate paintings of her are clearly all painted by the same artist). And you can't help but wonder what the relationship between de Vries and Martha is: how close were they? Did they go to school together? Has she been supporting him all these years, perhaps out of a sense of love? Oh, and the decision to shoot everything on video also lends the proceedings a welcome sense of visual uniformity. And I don't even mind the moving killer stones that much (even if there's no way they left those indentations in the ground near the TARDIS).
But despite the good moments, this simply isn't engaging enough to maintain interest. The neutering of any real threat in these two episodes leaves them without anything substantial to fill the void, and the net result feels like an hour of running around, rather than anything of note. It's an entertaining enough run-around, but it's also a lightweight one.
105 Actually, the cast and crew realized at some point that this was going to be the show's 100th story, so a scene was inserted where Romana and K-9 present the Doctor with a surprise birthday cake and a new scarf for his 751st birthday; however, producer Graham Williams nixed this scene on the (sensible) grounds that it was too self-indulgent.