Tommy Mayfield (John Stride) and Sir George Carrington (John Carson) are watching a test flight of Mayfield Industries’ newest fighter plane, the Mayfield Kestrel. Although it outclasses the German ME-109, Sir George explains that the government isn’t too keen on giving Mayfield money for development due to that shady “Japanese business” wot nearly brought the government down.

Mayfield complains bitterly that he was exonerated, and tells Sir George that he’ll prove his trustworthiness to the government by, er…

*checks notes*

…inviting suspected German spy Joanna Vanderlyn to his house for the weekend and catching her red-handed as she steals the plans for the Kestrel he intends to use as bait.

Can’t accuse Tommy Mayfield of half-measures, that’s for damn sure.

Meanwhile, back at Moustache Central, Poirot is explaining the finer points of using petroleum jelly on patent leather to Our Man Hastings, who’s on the couch wondering how to calculate cubic whatsits (his word, not mine). It seems Our Man is attempting to date…

*checks notes again*

…an architecture student?

Er… OK, a.. student, I guess, but he finds they don’t have much to talk about. In fact, she keeps being “out” every time he stops by, and consequently he ends up having tea with her mom.

Miss Lemon interrupts this increasingly creepy conversation by telling M. Poirot that a woman keeps telephoning but because she won’t give her name Miss Lemon refuses to put her through on the grounds that with no name she won’t know where to file her in her system. At this point, I’m already:

ANYWAY. Anonymous caller tries again, gives her name as “Smith”, thereby fulfilling The Lemon Test Of Nomenclature and asks Poirot to meet her. They meet at the Penguin Pool at the London Zoo (and there’s a pretty terrific sight gag with Poirot’s attire and stance being very penguin-like) where A) Our Belgian gets weirdly miffed she’s not wearing a green carnation as agreed upon, B) Smith even more weirdly tells him it’s because she doesn’t like wearing green, and C) Smith reveals herself to be Lady Mayfield (Ciaran Madden).

She’s worried that her husband’s bitterness will make him “less careful than he ought to be” this weekend, and asks Poirot to join them.

Poirot does, and finds that Sir George, his wife Lady Carrington and their son Reggie are also there. Vanderlyn (Carmen du Sautoy) arrives sporting a fabulous shimmering silver dress and a decidedly less-fabulous overwrought American accent.

Everybody has dinner, then it’s off to the lounge for cards and port. Mayfield’s assistant Carlyle goes to the study and takes the Kestrel plans from the safe, laying them out on the desk whilst a Desk Fan Of Ominousness +2 blows over them, rustling the pages.

(Seriously, they repeat the Pages Rustling In The Fan-Generated Breeze shot at least three more times, and for the life of me I cannot understand why, unless they’re trying to create tension around whether or not the plans blow off the table and under the desk? Which… let’s just move on.)

Poirot leaves cards to take a walk in the garden, where we meet Our Man Hastings, lamenting that Poirot has made him hole up in the town pub for the weekend. Hastings mentions that Inspector Japp is also there, though Poirot doesn’t know who invited him. We also learn that Hastings and Japp have to share a room and a bed.

Meanwhile, Mayfield and Sir George are also walking about the garden, when they see Mrs. Vanderlyn inside the house retrieving her purse from the lounge. Mayfield says he sees someone running along the terrace, but Sir George says there’s nobody there. Returning to the study, Mayfield exclaims that the top sheet of the plans is missing – the critical engineering formulas for the Kestrel.

(No, nobody checks to see if it just blew off the table.)

Sir George mutters, “Well done,” to Mayfield, who angrily tells him that “this wasn’t part of the plan”. Zut alors!

Japp comes round and arrests Vanderlyn. Poirot is insistent that only he, Mayfield, Carlyle, and Sir George could have taken the sheet.

After searching Vanderlyn’s room and person and finding nothing, she leaves the next morning – but not before Carlyle hands her a suitcase in a lovely shade of MacGuffin that she must have forgotten.

She drives away, and Poirot and Hastings steal a police car (just don’t, OK?) and trail her to the house of the German Ambassador, where she’s greeted by a hearty heil or two, a German shepherd (of course) and hands over the suitcase presumably containing the plans! She then… uh… drives off, I guess.

Has Mayfield’s plan backfired? Has one of the other guests helped themselves to the top secret plans? Is Vanderlyn really a German spy? Is the theft really, as the title proclaims, ‘incredible’? And will someone turn off that bloody desk fan?

Well, it was bound to happen sooner or later. This is one of the few episodes of Poirot that I’d call outright “bad“. The crime isn’t even really a crime. There’s a few halfhearted attempts at giving the other guests a motive, but nothing sticks in the least (and they’re all ushered off in the final 20 minutes anyway). The central conceit is given away in the first five minutes, so we’re already on guard for trickery.

What’s more, there are several extended scenes that just don’t go anywhere or do anything other than pad the running time; the Lemon v. Poirot discussion in the office, Vanderlyn’s search at the police station, the car “chase” with Hastings and Vanderlyn, everything at the house up until the time of the theft, and that Ominous Desk Fan – all of them go on uncomfortably long, and none of them are particularly entertaining.

And even though it’s nice to see Car Nut Hastings in action (they steal the police car because he’s pulled the spark plugs out of his own to tinker with it), there’s not much here for the cast to do other than stand around and wait for the mystery to resolve itself.

When a sight gag involving penguins is the highlight of your detective story, you’ve got some script problems, is what I’m saying.

Angels One Five!: The Mayfield Kestrel here is quite clearly intended to be a prototype of the Supermarine Spitfire. We know this because in the opening demonstration scene, the plane is recognizably a Spitfire when we see it banking and then strafing a truck.

Hey! It’s That Gal!: The lovely Mrs. Vanderlyn is played by Carmen du Sautoy, whom hardcore 007 fans will recognize as Saida the bellydancer from The Man With The Golden Gun.

Japp Of The Bakery!: Hastings notes that Japp talks in his sleep, apparently dreaming about catching criminals wielding desserts and bellowing things like “Stand back lads, he’s got a blancmange!”

Quotent Quotables:

Poirot: “Women do not wish to talk about Bernini and cubic thingamees.”

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Sir George: “Froggy thinks she didn’t do it.”

Poirot, not having it: “Froggy KNOWS she didn’t do it.”

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Mayfield: “Let sleeping dogs lie.”

Poirot: “No, no no – between the husband and the wife, there should be not the sleepy dogs.”

Next Week, on Poirot: Will a ruthless studio boss get what he deserves? Or will royalty get involved to complicate things with a love-beyond-their-stations narrative? Eh, a little of column A, a little of column B in… “The King of Clubs”!