Frank Langella has played many troubled and troubling characters during a recent career resurgence (Starting Out in the Evening, The Box, All Good Things), so it's a joy to see the actor's comical side (albeit bittersweet) in this absurdist yet soulful yoking of deadpan double act with a caustic commentary on old age.

Frank is a retired cat burglar put out to pasture in upstate New York, out of sight, but not quite out of the minds of his two children, who've got better things to do than deal with his encroaching dementia. Frank refuses to acknowledge his deteriorating condition and go quietly into a nursing home, so at wit's end, his son Hunter (James Marsden) shows up one day on Dad's door with an all purpose robot butler (voiced by Peter Sarsgaard) to take care of him.

Familial priorities are worryingly out of whack in this future world dependent upon robots to provide care and companionship as well as carrying out day-to-day chores. When Frank's hippie-dippie daughter Madison (Liv Tyler) briefly returns from bumming round the world, it's on the grounds of political vigilantism rather than giving the man who raised her some much needed emotional support. Madison deplores the new robot culture and is appalled by her brother foisting his responsibilities on to a machine, but reluctant to practise what she preaches, she's gone as quickly as she appears.

The best Frank can expect is from his children is be to cared for at arm's length, brother and sister occasionally phoning or dropping by to check in on him, more out of obligation than concern. With every right to be bitter and grouchy, it's hard to determine if Frank's kids made him this way or that's what turned his kids away in the first place (Hunter understandably, also holds a longstanding grudge over his father's career choice). Feeling moral disgust at those around him and physical disgust for himself, Frank sees humanity's selfishness and self-absorption plainly, mistrusting everyone. Within seconds of seeing his new robot carer, he's declaring it'll kill him in his sleep. We laugh at the blank, impregnable cut down, but the humour masks deeper hurt, a refusal to accept the next stage of his son's abandonment. Langella plays this perfectly, delivery so tart that it's double-edged with unperceived panic.

Thrown together and very much an odd couple, Robot's straight man routine finds humour in every exchange, Frank's curmudgeonly complaints about regular exercise and a healthier diet not computing with Robot's programming. In the same way, Frank's temerity in pointing out the ridiculousness of this domestic arrangement without apology to his uncomprehending assistant earns laugh out loud moments in the double digits. Peter Sarsgaard's synthesized robot voice benevolently winks at 2001: A Space Odyssey's HAL, with childlike enthusiasm. Delighting in his chores, you'd swear you could see a smile behind Robot's black visor when he announces it's time for Frank's morning enema.

Badgered into taking up a hobby that gets him out the house, Frank plays on Robot's lack of moral circuitry and non-judgemental logic, convincing him that a jewel heist is just what the doctor ordered in terms of mental and physical exercise. A willing accomplice with R2D2's knack for cracking locks, Frank imparts his larcenist's wisdom with the unmistakable joy of a father teaching life lessons to a son, spending their days together in ways he probably never did with Hunter. This seems to be the obvious place to explore and resolve some of the familial disconnect of the film's opening but Frank's mistakes as a father are rarely discussed, much less implied, an indication perhaps that this slight ninety minute film is missing a reel on the cutting room floor.

Hunter never gets the opportunity of seeing Frank through Robot's eyes and after initially deepening their rift, it feels natural that the automaton should be the intermediary to bring them back together. Director Jake Schreier misses an opportunity here, too caught up in the broad comic farce of a pensioner and his co-opted machine pulling off a heist. It's a step in the wrong direction, as if the paring of a codger and a can-opener wasn't already high concept enough. Such farce is ripe for Frank's acknowledgement that he and his Robot are both lacking a certain flexibility the job requires. Recruiting some young blood in the form of Hunter is the probable way of giving father and son a second chance, but screenwriter Christopher Ford doesn't take the bait. Ford doesn't develop their relationship beyond the inciting incident for fear of coming across as sentimental and feigning cheerfulness not in keeping with his protagonist. Instead he pads out the running time with a romance that goes nowhere (Susan Sarandon as the local librarian) and throws in an overly cruel last act twist that cheapens the script's emotional truthfulness. Up until this moment the film's deft tonal balance is commendable, convincingly weighing an outlandish premise with a rueful mediation on ageing, even if it's not quite sophisticated enough to fuse the two in a way that's narratively satisfying.

Nevertheless, Robot & Frank remains a thoroughly charming oddity, anchored by a spiky lead performance full of heart and humour below the wiry surface. An instantly iconic curmudgeon worthy of Matthau and Eastwood, it's a delight to see character actor Langella in a lead role – never mind one so unexpected as this – and a testament to his abilities as a performer that acting against someone in a suit and reacting to lines read off camera, this one man performance on set generates sparring buddy comedy chemistry on screen.

Timothy E. RAW talks to associate producer Theodora Dunlap, producer Sam Bisbee, director Jack Schreler and lead actor Frank Langella the film at the 2012 London Film Festival for Cine Outsider. Film clips courtesy of Momentum Pictures. The video has been optimised to be viewed full screen at 720p, or better still 1080p, which can be selected in the settings pop-up in the control bar.