The clever lads over in Classic Capitology can’t honestly claim to have seen the whole of the next story in their arsenal. That doesn’t mean they didn’t get this particular job done, as they most certainly did, but rather this story, more than any in the whole of Doctor Who canon, simply, and with unique consistency, bores them to sleep.
It is the Hartnell story The Web Planet.
In actuality, The Web Planet is not so much a failure as a misbegotten experiment. Not unlike The Edge of Destruction there’s more than a few initial touches of weirdness going on in the first couple of episodes, but eventually that gives way to the internecine battles between giant bees, beetles, moths and such. The Tardis travelers get separated, as they must, amongst the warring factions, but at six episodes The Web Planet goes on far too long to sustain interest, even for the hard core fan it must be confessed.
The next stop in the Classic Capitology quest puts the B in BS.