• title card: SQUARE ROOT OF EVIL superimposed on a reel tape recorder (recreated by Richard McGinlay)

Series 1 — Episode 3
Square Root Of Evil

by Richard Harris

Production completed: 21 January 1961. First transmission: 21 January 1961

TV Times summary

The corpse and the “Cardinal” turn Steed into someone whom the lovely Lisa may prefer dead

The following episode summary is written from the original scripts as this episode is now lost. There may have been changes made during filming.

Plot summary

Steed impersonates the forger Riordan, which allows him to join a crime syndicate that prints forged banknotes. Having uncovered their plans, he finds his every move being watched by The Cardinal - the second-in-command. Only the pretence of an injury eventually allows Steed to visit his Doctor’s surgery and Dr Keel ensures that The Cardinal and the rest of the gang are arrested.

show full synopsis

show plot summary

Prologue

A car speeds along a deserted country lane in blackest night, as it passes by, a door opens and a man’s body is flung out, tumbling into the ditch at the side of the road.1

Act 1

Steed’s boss, “5” (Heron Carvic) informs him that another agent, Tobert, was found dead while investigating a forgery racket run by Charles Hooper and Jimmy Bishop, AKA “The Cardinal”. 5 orders Steed to impersonate Timothy Riordan, an Irish master forger that Hooper has recruited; Riordan is due to be released from prison in three weeks.

John Steed (Patrick Macnee) is pensive about being 6", taller than Riordan, but 5 believes none of the gang have ever met him. 5’s secretary (Cynthia Bizeray) leads Steed to the records room and, fending off Steed’s sexual advances, plays a film of Hooper’s gang so Steed can identify them.

Steed is picked up outside Wandsworth Prison by Steve Bloom (John Woodvine) and taken to Hooper’s print shop to meet the gang. At the print shop, Jackie Warren (Vic Wise) has just finished a stack of £18,000 worth of forged notes when Steed and Bloom arrive.

Hooper (George Murcell) tells Steed that their printing plates are wearing out and he wants him to make new ones. Steed claims he’s going straight and isn’t interested – until Hooper shows him one of their notes and offers £10,000. The Cardinal (Alex Scott) enters, wearing his fedora pulled down to obscure his face.

CARDINAL: So you’re Riordan.
STEED: Who’s the poor man’s Al Capone?
HOOPER: This is Jimmy Bishop. He’s my righthand man.
CARDINAL: You’d be wise to remember that Riordan.
STEED: Somehow I can’t see you letting me forget.

Steed has annoyed The Cardinal and tests Steed’s bona fides with regard to knowing the prison he supposedly just left. Steed passes the test so they show Steed the set-up, and Hooper confesses they haven’t distributed any forgeries yet. Steed finally agrees that he’s in on it and is startled when The Cardinal says he has a surprise for him - one of his old girlfriends, Lisa, is outside in the car! Lisa (Delphi Lawrence) is brought in and she greets him effusively. Steed kisses her deeply then, knowing it’s a trap, turns to The Cardinal and tells him to stop playing games, he’s never seen Lisa before in his life!

Act 2

Warren is at his flat, discussing a post office hold-up with Steed and reveals that he used to run a legitimate wedding stationery business. Steed asks why he doesn’t live above Hooper’s garage and learns they were all kicked out when The Cardinal turned up; Warren is wary of The Cardinal because he carries a gun; he’s a bit too hard core gangster for him. Steed departs, claiming he’s going to place a bet on the dogs but actually rings 5, informing him that he’s infiltrated the gang and The Cardinal tried the phony girlfriend stunt, using his wife. Steed plans to check out the safe that night as The Cardinal and Hooper will be away collecting the next load of paper.

Steed arrives at the garage and enters to search the safe, unaware that someone was in one of the cars and is now silently following him. As he leaves, the lights come on, revealing Lisa who confronts him. She tells him she might not tell The Cardinal what he’s doing, but she knows he’s not Riordan.

STEED: Why didn’t you say anything then?
LISA: Because ... because I knew what it would mean. I met The Cardinal two years ago. He talked big and threw money around and I was impressed enough to marry him. When we moved in here with Hooper, I knew he was in some sort of racket but ... it didn’t matter. But now he’s changed. He’s vicious - suspicious of everybody. And he’s started carrying a gun.

Steed warns her that he has “enough evidence to make things red-hot for all of you”.

Hooper and The Cardinal return and Steed goes to spy on them. He overhears Jimmy saying that he doesn’t like the gang getting larger, and wants Hooper to tell him more about the operation. Steed watches them stacking the paper but then a truck loaded with paper runs into the bench where he’s hiding, injuring his hand. After escaping quietly, holding his hand to lessen the pain, he tells Lisa to go back to her room and say nothing. However, realising Steed is about to be caught as Jimmy returns, she deliberately makes a noise, drawing Jimmy’s attention. He cruelly hits her for sticking her nose into things that don’t involve her. Hooper protests, and Steed has to fight the urge to intervene.

Act 3

Steed visits Dr David Keel (Ian Hendry) to get his cut hand fixed, asking Carol Wilson (Ingrid Hafner) for a large Scotch to take away the pain. He’s worried about Lisa, if she hadn’t shown herself when she did, Keel would be dealing with a corpse instead of a cut hand. Steed calls 5 and tells him Dr Keel has been told about the case in case they need him, and he’s dropped off some film at the chemist. Hanging up, Steed gives Keel 5’s number - WHItehall 0011 - as Carol prepares an antibiotic injection for his hand.

Lisa learns that Jimmy is suspicious of Steed and had heard Steed was seen with a plain-clothes copper the previous night but Lisa persuades him Riordan wouldn’t throw away the money for those who put him inside. Hooper arrives and calls the gang into his office, angrily telling Jimmy to get out of his chair. He announces the boss will collect the money that night. Bloom is concerned as they’ve only done half the job and Hooper explains the boss planned it that way to stop loose talk; the job is complete. Steed complains they haven’t used him yet and won’t get any money but Hooper promises him half they offered, or the full amount if he stays on for the next job. He then orders them all to crate up the presses as they’re moving the whole operation.

Steed goes to call Keel, saying he needs both his hands, but The Cardinal doesn’t want to let him, saying as soon as they talk about moving he wants to make a phone call. Hooper agrees but finally decides to call Dr Keel on his behalf. When Hooper hears he has rung a real doctor he lets Steed take the phone.

STEED: (DISTORT) My name’s Riordan ... it’s about an appointment I have with the doctor ...
CAROL: Mr. Riordan? I don’t ..
STEED: (DISTORT) I’m a new patient. I came for the first time this morning. Mr. Steed recommended me.
CAROL: [LAUGHS] Oh, it’s you. Scotch this morning, Irish this afternoon.2

Steed manages to pass on a warning to Keel by saying his “firm won’t let him go” and they will “be working very late”. Dr Keel immediately calls 5 to deliver the message. 5 doesn’t want to make a move as they’re after the man behind Hooper so he asks Keel to visit the garage to see what’s going on while he organises a discreet police cordon.

The gang are packing up when the door bell rings, making them jumpy. It’s Dr Keel, who Hooper leads into his office. He goes to give Steed another injection but The Cardinal doesn’t buy it and orders them down to the print room at gun point. He tells Hooper he never trusted Riordan and now the doctor’s seen too much there’s only one thing to do. Jimmy says to Steed, “If you’re one of us - kill him”. Steed refuses and points the gun at Jimmy instead. The Cardinal sneers at him and shows the cartridges in his hand, the gun is unloaded. He launches himself at Steed with a roar and they fight, Keel and Lisa siding with Steed and Warren and Hooper with The Cardinal, employing printing equipment as weapons. With the gang rounded up and Lisa allowed to go free,3 Steed muses that they can catch the real “Number 1” by replacing the gang with some of their own boys.


  1. This film insert seems to have been reused in Toy Trap when Lennie is killed.
  2. Carol’s joke is in reference to Steed asking her for a large Scotch to take away the pain when he visited earlier, and the Irish accent he’s using when impersonating Riordan.
  3. The details about who joined the fight and Lisa being allowed to go free come from The Complete Avengers by Dave Rogers (Boxtree/St. Martin’s Press First U.S. Edition paperback, 1995, p. 19) but are not in the camera script, other than Steed telling Jackie Warren the party is over at the end.

Support this site via Paypal Join us on Facebook Become a Patreon! Fan forum