Doctor Who/Recap/S30/E07 The Unicorn and the Wasp

"Agatha: Agatha Christie.

Donna: What about her?

Agatha:...That's me.

Donna: No."

The Doctor has brought Donna to the twenties for a nice garden party. Meanwhile, a Professor Peach is murdered, in the library, with the lead pipe.

Also at the party is Agatha Christie herself. Pity she won't remember it: the date is 8 December 1926, and Agatha will mysteriously vanish and turn up ten days later, confused and with no memory of where she'd been. Which means that whatever freaked out (not-yet-Dame) Agatha is about to happen. But right now, there's a murder to be solved!

"Agatha: Someone should call the police.

The Doctor: We don't have to! Chief Inspector Smith from Scotland Yard. Known as "The Doctor". Miss Noble is the plucky young girl that helps me out."

But who murdered Professor Peach? Was it The Flapper? The Vicar? The Colonel? The mother? The two secretly gay men? The Doctor and Donna are both delighted to be solving a murder mystery together with Agatha, but Agatha reminds them that (a) she only writes books and she knows nothing about actual crime solving, and (b) murder is not funny and could they please stop squeeing.

Over the course of an afternoon of wacky hijinks that cleverly recall the titles of many of Christie's works (seriously, try it as a drinking game!), the Doctor, Donna and Mrs. Christie all piece together a story of forbidden love, murder, secret identities, abandoned babies and alien bling. In the end, it turns out that the killer (a giant alien wasp) was telepathically linked with someone reading a Christie book, which explains why the world suddenly started behaving like a Christie book.

Also, Donna snogs the Doctor, but it makes sense in context and he tasted like anchovy.

Tropes
"Professor Peach: I say... what are you doing with that lead piping?"
 * The Alcoholic: Mrs. Eddison spends a very good fraction of her screen time holding something alcoholic. Including that time she said it was tea.
 * All the Good Men Are Gay: 'All the decent men are on the other bus.' 'Or Time Lords.'
 * Big Creepy Crawlies
 * Big Secret: Lots of them. Lady Eddison's Mysterious Past, Colonel Hugh's able-bodiedness, Miss Redmond's real identity, and Roger's relationship with the footman.
 * Bizarre Alien Biology: The Doctor's ability to reverse cyanide poisoning using various substances. Actually some of the Techno Babble he spouts is vaguely plausible.
 * Bitter Almonds
 * The Butler Did It: Lampshaded but averted; "At least we know the butler didn't do it".
 * The Cameo: The Very Rev. Sandy McDonald, David Tennant's father, plays the footman at the beginning: he's the one in the foreground when Donna orders a "sidecar".
 * A different footman from the one with whom Roger is in a relationship, by the way.
 * Changed My Jumper
 * Chekhov's Gun: The big, dorky magnifying glass is a pretty short-term one; after the Doctor gives it to Donna, she ends up using it about ten minutes later to hold off the giant wasp.
 * Classy Cat Burglar: The Unicorn, although she gets a lot less classy when she's exposed.
 * Continuity Nod: See Lampshade Hanging.
 * Donna attempts at affecting a High English accent when meeting Lady Eddison... only to be told by the Doctor not to do that.
 * We find out where The Doctor put the Carrionites: In a chest for all things that start with the letter C, which also included a Cyberman logo.
 * Enemy Within
 * Elephant in The Living Room: Agatha's just learned of her husband's affair, but doesn't want to admit to it(see Stiff Upper Lip).
 * Flash Back Back Back: The interrogated suspects have flashbacks (complete with wavy line dissolve) while establishing their alibis, revealing that none of them are exactly truthful. Then played with when the Colonel has a flashback within a flashback. Then the Doctor has a flashback of his own....
 * Foreshadowing: Possibly,
 * Within the episode:
 * Genre Blind:
 * Genre Blind:

"Butler: I beg your pardon?!?"
 * Genteel Interbellum Setting
 * Getting Crap Past the Radar: The 1920s porn. That got more questions from the kids than the gay relationship.
 * The Doctor asks the (closeted gay) butler for ginger beer -- cockney rhyming slang for "queer".

"Donna: I mean... Professor Peach, in the library, with the lead piping?"
 * Giant Flyer
 * Half Human Hybrid
 * Historical Domain Character: Agatha Christie.
 * Historical in Joke: Christie's historic disappearance.
 * Interspecies Romance: Lady Eddison and Christopher the Vespiform.
 * In the Past Everyone Will Be Famous
 * Involuntary Shapeshifting
 * I Want Grandkids: The Colonel comments that he and his wife are unlikely to have grandchildren, implying that he knows about Roger's sexual orientation.
 * Lampshade Hanging via a Continuity Nod: Donna finds the idea of Agatha Christie being involved in a real murder mystery as ridiculous as the idea of finding Dickens surrounded by ghosts at Christmas. The Doctor looks embarrassed, probably recalling the events of "The Unquiet Dead".
 * Magic Pants: Apparently Vespiforms can transform their clothes too when they take on human form.
 * Meaningful Name: Professor Peach, and possibly Miss Redmond, are Cluedo (Clue for our American readers) references. In fact the Cluedo-ness of the situation is lampshaded by Donna.

"Agatha: Actually, I was going to say you're completely innocent. Sorry."
 * Mistaken Confession: As Christie and the Doctor expose the house's secrets, the Colonel cracks and admits he doesn't need his wheelchair... much to their surprise.

"Ever so nice to meet you, I don't fink."
 * Never One Murder
 * NOT: The Unicorn, in the more antiquated version.

"Agatha Christie: The Unicorn. He’s here!
 * The Noun and The Noun
 * Ooh, Me Accent's Slipping: After the Mistaken Confession, Agatha, completely taken aback, slips from RP into Fenella Woolgar's Estuary English.
 * Overly Long Gag: See Suspiciously Specific Denial.
 * Parlor Games: Charades, after the Doctor gets poisoned.
 * Pass the Popcorn: Donna seems to be doing this during the drawing-room reveal, though we can't see what it is she's eating. Some glances show that it may be green grapes.
 * Purple Rocks: The alien jewelery.
 * Rummage Fail: At the very end, the Doctor digs through some of his junk in the TARDIS (of the starts-with-a-C variety); before he finds his copy of Death in the Clouds, he pulls out the C logo off a Cyberman's chestplate, the head of a statue, a crystal ball full of Carrionites (still screaming) and a big jumble of cables.
 * Running Gag: The one about the Doctor and Donna not being married and the one where the companion attempts an accent, and the Doctor tells her not to.
 * Hilariously enough, the protestations turn out to be unnecessary; Christie noticed Donna didn't have a wedding ring.
 * Shoot the Dog: Or rather, Drown the Giant Wasp.
 * Shout Out: Rusty and Gareth Roberts had a bit of fun with the script. Gareth would pop a reference in, send the draft to Rusty, and it'd come back with another one, and so forth. All told, there are about 15 titles of Agatha Christie novels directly referenced in dialogue. Such as...
 * And Then There Were None
 * N or M?
 * Crooked House
 * Taken At The Flood
 * Endless Night
 * Cat Among the Pigeons
 * Cards on the Table
 * Death Comes As The End
 * Murder at the Vicarage
 * They Do It With Mirrors
 * The Murder On The Orient Express
 * Why Didn't They Ask Evans?
 * Nemesis
 * Sparkling Cyanide
 * The Body in the Library
 * Appointment with Death
 * The Moving Finger
 * They also have The Man In The Brown Suit solving the mystery of The Body In The Library. The reveal scene has the Doctor doing The Moving Finger. The Doctor also has a copy of Death in The Clouds edited in the year 5 billion and then some, no less.
 * And in a non-Christie Shout Out, Colonel Hugh's getting up from his wheelchair is from The Real Inspector Hound.
 * At the beginning, a guy with a colour-related name is murdered in the library with a lead pipe. Lampshaded by Donna, even. (See Meaningful Name)
 * Stealth Pun: At the end of the episode the Doctor pulls things filed under 'C' from (what else?) a sea-chest.
 * Stiff Upper Lip: "She's British and moneyed. That's what they do; they carry on."
 * Stigmatic Pregnancy Euphemism: In this case,
 * Summation Gathering
 * Suspiciously Specific Denial: "Oh, yes, all alone. Totally alone. Absolutely alone. Completely. All of the time. I wandered, lonely as the proverbial cloud. There was no one else with me; not at all! Not ever!" *flashback shows him flirting and holding hands with his footman*
 * The Theme Park Version: The writer deliberately went for the popular perception of a Christie novel as opposed to what they're actually like.
 * Title Drop of the episode:

The Doctor: The Unicorn and the Wasp..."

"The Doctor: Donna, that thing couldn't help itself."
 * Troperrific: And the Doctor clearly knows, and is loving every moment of it.
 * Unreliable Narrator: About half of the "Where were you at a quarter past four?" flashbacks don't really match what the character says they were doing. Usually hilariously.
 * Unstoppable Rage: Murder at the vicar's rage (*ahem*) when the boys are stealing things from the church.
 * Vertigo Effect: On Lady Edison when she realizes.
 * The Vicar: Subverted; he starts out looking like the embodiment of the trope, but then...
 * Wazzzzptalk: "Put thozzzzzze thingzzzzz back where you found themzzzzzzzzzZZZZZ!"
 * What the Hell Hero