Since I didn't get a chance the past three weeks to review individual episodes, this is going to be a three-review mash-up. Enjoy.
The Witch's Familiar
What? You want more? Okay, I'll refrain from boring you with unnecessary details and cut right to the chase. Clara has been dumbed down this series into a simpering, comic relief moron of a sidekick. Waking up after being seemingly disintegrated by a Dalek death ray in the previous episode, Clara discovers how Missy survived her apparent death in Death In Heaven basically by going through the same trick herself, or more accurately, getting dragged through it. So that's one extremely rare explanation by show head writer Stephen Moffat. Too bad it's the only one given in five years, and likely to be the only one ever.
What I found unbearable was the dynamic between Clara and Missy as they set off to rescue the Doctor. The human should despise the Time Lady for turning her boyfriend into a Cyberman in Series 8, and there's a throw away scene in which she threatens Missy with a pointed stick, but it just doesn't feel genuine on screen. Clara is reduced to being the comedy relief, with Michelle Gomez as the Master in female form chewing up the scenes. Clara's presence is almost an afterthought here and it cheapens the character. This is especially true at the end of the episode when the Doctor, played by Peter Capaldi, rescues her.
The scene with the Doctor and Davros was meant to provoke tears but, again, the out-of-character nature of what turns out to be another of Davros' ploys to defeat the Doctor and grant his Daleks ultimate power just rings very false.
All in all, I give this episode a D-.
Under the Lake
Now this is much better than the two previous episodes of Series 9, and like them, is the first of another two-parter. The Doctor and Clara arrive in an underwater salvaging base in 2119, days after ghosts have begun killing members of the crew to add to their ranks. Upon realizing that the spectres are being used as transmitters to send a signal, with each murdered soul helping to boost the signal, the Doctor travels back in time to find out how it all started. That's when we get a damn good cliffhanger.
Episode writer Toby Whithouse did a splendid job spinning a ghostly horror yarn, providing scares but also whetting our appetites for what comes next, which not only continues the scares but also brings back an element of true science fiction. That brings us to...
Before the Flood
Whithouse has the Doctor start us off with a fourth-wall-breaking lecture by the Doctor explaining what is erroneously called the bootstrap paradox, in which a person, object, or event is performed by a time traveler who ultimately is responsible for making that person, object, or event come into being. The given example is Beethoven: The hypothetical traveler tries without success to locate his musical idol, and in desperation uses all of his collected sheet-copies of Beethoven's music to publish them in the past. The question then is, without an original creator, how did the music appear in the first place? But as I said, this is the wrong paradox, although writer Whithouse may be forgiven for having gotten it wrong as he is not a scientist. What he's actually describing is what I call the Terminator Paradox, in which traveling back in time to witness or alter past events actually results in causing events in the present to occur.
Anyway, the Doctor and two crewmembers from the base who came with him arrive in a soon-to-be-submerged military training town circa 1980, to locate the cause of the ghosts. The learn that a spaceship that was found in the previous episode is actually a hearse, and that its cargo, still very much alive, is responsible for starting the chain of deaths. The Doctor realizes he can't change events that are already set in stone, but tries to alter what he can.
As with Under the Lake, Before the Flood captures the emotions of the characters rather well, and we get to expand our minds with our share of science-y questions.
The only gripe I had was with two rather poorly written and improbable scenes in which characters who'd shown no previous attraction to one another suddenly declare their feelings. Come on, writer-people! You can do better than that!
I give these two episodes a B+.