Don’t trust your custodian? Blame Hollywood.

This is the year movies have sullied the reputation of janitorial staffs everywhere. First, it was Diane Keaton scrubbing toilets and swiping millions in the lightweight caper comedy “Mad Money.” This week, Sir Michael Caine plays a cleaning man who uses the anonymity of his after-hours profession to lift a fortune in diamonds with Demi Moore’s assistance in the crime-thriller “Flawless.”

True, a Moore-Caine coupling would have made more sense 20 years ago, when the actress was entering the prime of her career. (Caine is always on his game, no matter the decade.) But “Flawless” stretches back even further than 1988.

The story, penned by Edward Anderson and piloted by Michael Radford, takes place in 1960s London. Laura Quinn (Moore) is the lone female executive at prestigious London Diamond. Frustrated by the glass ceiling that keeps her from joining the company’s male-dominated board, Quinn listens to a pitch by kindly custodian Hobbs (Caine) who, with help, plans to loot the Lon Di vault of almost $2 million.

American heist pictures typically employ high-tech gadgets and massive, blazing guns. British counterparts like “Flawless” tend to take a more subdued track.

Radford stages dry scenes of bureaucratic, backroom hand wringing of the suits pinched by this crime. This opens the door for icy co-star Lambert Wilson (“The Matrix” sequels), who slices through the stuffy atmosphere as an investigator hired to put the pieces together.

“Flawless” is less a whodunit and more a how-did-they-do-it. It sticks to its routine and guards a great twist. But the answers to its most intriguing puzzles disappoint, and the final motive provided for this near-perfect scheme can only be described as flawed.