Knock Knock is a story which is defined much more by what is wants to be rather than what it is. That Knock Knock is a pastiche is no shame in the slightest, after all the backbone of Tom Baker’s early years in stories such as Planet of Evil and The Brain of Morbius or even The Deadly Assassin has clearly delineated sources and were quite successful variations on them.
But ultimately Knock Knock doesn’t quite work. The setup is way too abrupt, and the scares were easily foretold once the residents had settled in. And then there were the plot holes. How was the Landlord able to move around? Why 20 years between feedings? It goes on.
That’s not to say there aren’t a fair share of nice touches. Anything involving the consumption by the beetles or the wood are well done, and the realization of Eliza by Mariah Gale was superb–not wooden at all.