Professor Marcus (Alec Guiness), ostensibly a musician and academic, rents a London flat from a sweet old lady (Katie Johnson). He tells her that, from time to time, sereral other musicians will visit in order to rehearse. In truth, the professsor can't play a note and nor can his visitors: he's a criminal mastermind, holding court over his gang of thieves, including the likes of Harry (Peter Sellers). the homicidal Louis (Herbert Lom) and punch-drunk One-round (Danny Green). The gang use Professor Marcus' flat as headquarters as they conceive a daring 60,000 pound robbery.
