V6 - Coronas of the Sun

The story, admittedly, stalls just a little bit by around this episode, but only because of the circumstances thrust upon the writers at this point. The seventh episode, The Feast of Steven, was slated to go out on Christmas Day, and it had been decided in advance that it should be a, more or less, stand alone episode due to the holiday.

However, the story would pick up again in Episode 8 as if the Christmas episode had never happened (and, for international viewers, that would have been the case anyway as the Christmas episode was never intended to be included in the packaged story, thus making The Daleks' Master Plan an 11-part story outside of the UK. Of course, no country outside of the UK actually aired The Daleks' Master Plan anyway, so it was a moot point). So, Episode 6 basically had to end without too much of a cliffhanger so that it could seamlessly blend in with the beginning of Episode 8.

Thus, the Doctor and his companions pretty much have to find their way back to the safety of the TARDIS at episode's end and not be in any particular danger when they get there so that they can coast around for a week or so until the story was ready to pick up again. Thanks to an old standby that Terry Nation would use again - invisible monsters - the TARDIS crew escape the clutches of the Daleks and do, indeed, make it back to safety. The story then gets its MacGuffin to extend the length for a few more episodes as The Doctor crafts a fake taranium core that the Daleks won't have a chance to check for another couple weeks. Crisis averted! Well done, Dennis Spooner, in getting out of that one.