It is a murky day when Professor Marcus (Guinness) answers an advertisement placed by neighborhood busybody and widow Mrs. Wilberforce (Katie Johnson) of rooms to let in her slightly dilapidated house. The house might be old and musty, settling, and filled with screaming parrots,** but for Marcus, it's "location, location, location." And he is willing to negotiate with Mrs. Wilberforce in order to secure rooms for himself and his band-mates, a string quartet. As he explains, his orchestra needs rooms for practicing, but that is merely a ruse for a much darker purpose: his rather suspicious looking orchestra is actually less musically inclined as criminally disposed.
Besides Marcus, there is former pugilist "One-Round" Lawson (Danny Green) tough but a bit punch-drunk, spiv Harry Robinson (Peter Sellers), con-man Major Claude Courtney (Cecil Parker) and the murderous gangster Louis Harvey (Herbert Lom). They would never pass for a quartet if anyone had discriminating eyes, but Mrs. Wilberforce, who usually eyes things suspiciously, is quite myopic when it comes to the Professor's players. Maybe it's their repertoire of Boccherini's Minuet in E that evokes fond memories for her and makes her look past their bizarre looks.
What they have eyes for is the reason they took the rooms in the first place—the modest house is but a stone's throw from the King's Cross railway station that is the destination for a regular armored car delivery, it's cargo of cash being what they covet and the Professor's plans being how they will carry it off.The humor of the film is how these wolves must pretend they're sheep for the benefit of the innocent Mr.s Wilberforce. The crooks so their best (or worst) to be on their most innocent—or least suspicious behavior—around Mrs. Wilberforce and her friends, and the usually suspicious landlady is unaware that she has a bunch of thugs under her roof, despite sticking out like snapdragons in a rose garden. There is the constant state of danger that could become...very uncordial.
Then once the heist has been carried off without immediate consequence, there is the tense situation that the money might be detected. The ill-gotten gains are then at risk of being discovered by the kindly, if "Kravitzy" little old landlady. All of the main cast of characters, innocent or guilty as sin, are strangers in a strange land, potentially clashing with their own natures, due to the circumstances.
Now, because it is a crime film, albeit a comedic one, from the 1950's, some comeuppance—some moral balance—must be imposed in the way the story shakes out, one that has been played out with a similarly accidental twist in later movies of the type, but takes on a decidedly macabre version of "there's no honor among thieves". That there is still some ambiguity in that resolution is what makes the film quirky, ironic and mischievous. And jolly bad fun.
* The Coen brothers (Joel and Ethan) remade the film, set in the South (Louisianna, actually) with Tom Hanks playing the Professor character, but their film, though different in particulars, is not an improvement over the original. Perhaps the decision to re-locate the film in the States is a reaction to the fact that this very British film was actually written by American William Rose, who wrote such other films as It's a Mad, Mad, Mad, Mad World, The Russians are Coming! The Russians are Coming!, and Guess Who's Coming to Dinner.
** The parrots, amusingly, are voiced by Peter Sellers.
*** Guinness, when he was offered the script, remarked "but this is for Alastair Sim, surely" (yes, it was, but he'd turned down the part) and Guinness' character make-up design does bear a slight toothy resemblance to the actor. Sim—if you think he looks very familiar—played what many think of as the definitive Ebeneezer Scrooge in 1951's Scrooge—directed by Brian Desmond-Hurst.