• title card: white all caps text reading ‘BUILD A BETTER MOUSETRAP’ superimposed on the biker gang laughing as Ermyntrude tries to put a hex on them
  • Steed shows the gang a map of his proposed racing circuit
  • Jessy hugs Dave, who seems more interested in Cathy
  • The Peck sisters are frightened by the sound of motorbikes outside
  • Cathy stares at Cynthia’s unlikely contraption
  • The sisters are delighted to get their mousetrap back

Series 3 — Episode 21
Build a Better Mousetrap

by Brian Clemens
Designed by Douglas James
Directed by Peter Hammond

Production No 3610, VTR/ABC/2930
Production completed: August 28 1963. First transmission: February 15 1964.

TV Times summary

In which Steed visits two witches; and Cathy rides a motorbike to do the ton plus ten

Plot summary

Mrs. Gale becomes a biker to investigate what mysterious signal is jamming all mechanical devices in one area. Steed believes that the two daughters of Professor Peck have perfected his last incomplete invention but enemy agents have reached the same conclusion and Wesker steals the invention, which is recaptured by Steed. In reality, the machine is merely Cynthia’s attempt to build a better mousetrap!

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Catherine Gale (Honor Blackman) joins a motorcycle gang, proving herself by doing a ‘ton-and-ten’1 but when she goes to a watermill to ask for directions to Laleham’s Meadow, she and Dave (Donald Webster) are sent away with a flea in their ear by the two elderly sisters who live there. Cynthia (Athene Seyler) says she must have quiet for her work and will stop them; when the gang laugh at her, Ermyntrude (Nora Nicholson) threatens to put a spell on them to stop their motorbikes.

Act 1

John Steed (Patrick Macnee) installs himself at a nearby pub, run by the morose Harris (Harold Goodwin). While waiting for Stigant (Allan McClelland), a scientist from a nearby nuclear plant, he meets Colonel Wesker (John Tate) and his daughter Caroline (Alison Seebohm) who are also staying there. Stigant arrives and Harris complains about him stopping the clocks and the refrigerator. Stigant insists the plant has nothing to do with the mechanical failures. He explains to Steed that for the past two months there have been intermittent failures of all electrical and mechanical equipment in a local two mile radius — even his car, which he checked thoroughly and found no mechanical failure. The failures only last for an hour or so. He wishes they were building the fiendish device the local villagers think they’re making, a device that could stop all machinery would have enormous military potential. Stigant concedes that there is a correlation with the arrival of motorcycle gangs, looking to let off steam in the countryside, but he thinks it co-incidence.

Dave’s gang arrives in a roar of engines and head into the barn. Steed befriends their leader by claiming to know the man who built his ‘sickle’ and learns they’ve started having trouble with their bikes since using Laleham’s Meadow. Dave’s girlfriend, Jessy (Marian Diamond) says it’s the two old ladies, but Dave is annoyed with her for says anything and thinks it’s daft. Cathy then slips away from the gang and confers with Steed.

STEED: So you broke through the age barrier with a ton plus ten.
CATHY: Anyone over twenty is ancient — over thirty — might as well be dead.

She tells him Dave is fair minded with a strong sense of right, and ironically old fashioned. She confirms that the bikes just stop dead and the old ladies in the watermill did threaten to put a spell on them — and Steed wonders why Dave tried to stop Jessy telling him.

Cathy returns to the gang while Steed procures a map of the area from Harris. He’s just unfolded it when Caroline’s hand is suddenly on top of his, caressing it gently.

CAROLINE: Looking for a little secret place?
STEED: I was… studying the area — for our ride … I don’t want you to mislead me.
CAROLINE: Would that be possible?
STEED: (LEANING IN TOWARD HER) I have a very poor sense of direction.

Steed prises himself away and returns to the barn, then cons the cycle gang into riding a point-to-point around the area for a prize of £252 to the first ones back, each travelling a different route.

At the mill, Ermyntrude hears the approaching motorbikes and Cynthia ducks behind a curtain, and then they hear the bike engines conking out.

ERMYNTRUDE: Do you think we’re very wicked?
CYNTHIA: Wicked? Wicked? Nothing of the kind. We have a moral right, Min. How peaceful it is. So peaceful.
ERMYNTRUDE: Wicked, Cyn. Wicked. A century or more ago we could have been burned as witches.

An angry Cathy trudges back over the fields after breaking down and finds Steed has already deduced where she broke down. He shows her the bikes were only affected within a certain radius and uses the resulting mechanical failures to pinpoint the location of the engine-jamming — the old watermill!

Act 2

The next day, Harris tells Steed the two old women are witches and he wouldn’t dare go near their mill — Ermyntrude is timid, all lace and button boots, while Cynthia is forceful with a booming voice, and he pointedly warns him to stay away.3 Nonetheless, Steed asks both Stigant and Cathy to find out about the ladies. Caroline come in, predatorially looking for Steed but he makes his excuses and leaves.

A while later, Cynthia is stirring a huge cauldron when Ermyntrude screams that she’s seen a mouse. Cynthia leaps into action, saying they need a live mouse and must catch it.

CYNTHIA: It’s exactly what we want, we must catch it. Get a branch… You’re sure it want over here?
ERMYNTRUDE: Yes … it was … immense!
CYNTHIA: A rat! It’s better still … Come along, help me catch it!

Steed arrives at the mill, posing as an inspector from The National Distrust4

STEED: Well, it’s a fairly new organisation — allied to the National Trust … but different … different … Now the National Trust trusts people to look after buildings of national interest — but we don’t — oh no, we don’t trust anybody at all — far from it — National DIStrust, you see? Now, that’s why we inspect. The whole body of our licenced inspectors go all over the country, making quite certain that people look after their places.

Cynthia says the mill was only built in 1870 and isn’t historic so Steed is shooed away having learned nothing while Cynthia scurries back to check on her ‘mechanism’ — as he leaves, there is a loud bang from inside. Steed steals a rose from one of the bushes outside for his lapel5 and as he goes Dave emerges from behind the mill wheel and investigates the area…

Steed returns to the pub barn where Cathy is hanging out with the gang. Dave returns shortly after and makes Jessy jealous by gazing at Cathy as he avoids her questions about why he went to the mill.

Steed takes a call in the pub, observed by Caroline who is sitting nearby. He arranges to meet Stigant at the mill, who has learned that the women are Professor Peck’s daughters. Cynthia and Min meanwhile have discovered the National Distrust doesn’t exist and are on their guard against spies and prowlers. When Steed arrives he’s set upon by Gordon (David Anderson). He fights him off after getting a good look at Gordon, who beats a hasty retreat. Steed turns back to the water wheel and discovers Gordon has already killed Stigant.

Act 3

Cynthia emerges from her lab after a few hefty blasts, her face covered in soot. She’s beaming as she tells Ermyntrude she used a bit too much nitro-glycerine, but she’s nearing perfection. Inside, a strange device with whirring cogs and spindles as she adjusts it and she tells Min it’s for the world, for its betterment, and she cannot brook any interruptions.

Steed returns to the pub and informs everyone of Stigant’s death. Colonel Wesker blames the bikers for the murder while Harris declares he was killed with witchcraft. Dave meanwhile has twigged that Cathy is up to something and, like him, is interested in the watermill. While they dance in the barn, they arrange to investigate the mill, twisting past Caroline who is dancing with some of the boys.

Wesker meanwhile is complaining to Steed about being put out to pasture by the War Office when he still had a lot to offer6. When he stomps off for his evening stroll, Cathy sidles up and tells Steed that Dave has found the side door of the mill has a faulty lock;7 they’re going to break in while the sisters are at the evening service.

STEED: Right, I’ll give you ten minutes start, then I’ll follow you, just in case.
CATHY: In case of what?
STEED: Dave showing more initiative than is good for him.

Cathy returns to the barn but finds Dave has already left. When she asks Jessy if he’s gone for a ride she burst out into a jealous tirade.

JESSY: He’ll come looking for you I expect. He’s all over you for the first few weeks. That’s the way he opera— (SOBS) Why’n’t you stay with your own kind?
CATHY: Jessy, I think you’ve got hold of the wrong end of the stick.
JESSY: We had fun before we came to this place. Nothing’s the same anymore. I don’t know why you joined this gang.
CATHY: Jessy, I have to go out now.8

As Cathy starts her bike, she’s joined by Dave, visor down on his helmet, who leaps on the next bike. They ride away together into the darkness…
After she’s gone, Harris turfs the gang out of the barn for the night and turns to find Jessy still there, crying to herself. He scares her when he tries to console her, then repels her when he tries to become friendly and creepily says he’s watched her more than anyone else.

Steed is about to follow, but a simpering Caroline intercepts him at the bar and drugs his whisky. Steed has been suspicious of her for a while and pours the drink into a pot plant over her shoulder as he embraces her. Steed then pretends to pass out. She laughs as he collapses then shouts “Nyet!” as he raises a hand for help. As soon as she’s gone, he gets back up and says to the plant, “Now you have a good night’s sleep.”

Steed makes Jessy read his telegram to see what’s really going on — the Professor had developed a projected magnetic field mechanical jammer before he died, and his daughters are confirmed to be living in the mill. Meanwhile, Cathy finds Cynthia’s device and her companion raises his visor, revealing himself to be Colonel Wesker instead of Dave, and pulls a gun on her.

Harris and Jessy find Dave bound and gagged in the loft. Steed realises that Cathy’s in danger, and after making sure Dave’s not still too groggy, rushes to the mill with Dave.

Back at the Mill, Gordon and Caroline arrive and Wesker gloats over capturing the device. Just then the sisters return home, giving Cathy the opportunity to attack Gordon, knocking an innocuous looking bit of electronic equipment to the ground. Steed and Dave turn up and apprehend Caroline and Gordon but Cathy says Wesker has escaped with the device.

CYNTHIA: He did no such thing! The jamming device as you call it is still here. Completely shattered, broken — and no chance of replacing it … poor Papa.

Cynthia goes on to tell them the Colonel has made off with her own life’s work, so near completion. Steed urgently asks what her invention was, but isn’t ready for Cynthia’s answer:

CYNTHIA: My mousetrap. All these years I’ve been trying to build a better mousetrap.


There’s an explosion outside, and Wesker is found lying on the ground holding it, his face covered with soot.

CYNTHIA: My mousetrap!
STEED: It seems to be equally effective with the larger rodents. But don’t you think you’re using too strong a cheese?

  1. That’s 110 miles per hour — 177 kmh in metric, so blisteringly fast. Dave mentions that the club is called the ‘Salts’ because they go like a dose of — everyone in the club has to have done a ton plus 5 (105mph/169kmh).
  2. Not worth it, you say? That would be £520 today.
  3. A classic red herring, as we’ve already had several shots of Harris acting suspiciously. As Steed tells Cathy straight after, the warning could have been meant in a friendly fashion, or otherwise.
  4. A lovely bit of bureaucratic humour, citing “structure 447/9 code B”, and “the stipulations in Form A47”, from the “Ministry of (cough)” and flashing credentials so fast they’re unreadable.
  5. A minor theme for Series 3, he did the same in The Undertakers.
  6. Bitterness at a stalled or terminated career is a red flag for counter-espionage agents, so Steed would have suspected the Colonel and Caroline at this point, if he hadn’t already.
  7. Steed says, “So that’s what he was doing”, so was clearly aware Dave was there when he first visited the mill.
  8. It’s very angst-ridden teen drama, isn’t it? This end of this scene was changed, as Cathy exits stage left after a gang member pushes between her and Jessy. The original script had this final exchange to deepen Jessy’s jealousy, but the lines were cut:
    JESSY: With Dave?
    CATHY: Yes, with Dave.

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