Steven Russell is living a lie – several of them, in fact. Given up for adoption in his infancy by an indifferent mother, he is living a Norman Rockwell version of the American dream, with a worshipful, Jesus-loving wife, an adoring daughter and a quaint home in the Georgia suburbs. He even plays piano for the church choir.

But Steven is no angel, nor does he aspire to be. The family, the job, the evangelical zeal – it’s all a front for a shifty, rudderless man searching for an identity, bored by the simple life and hiding his homosexuality behind a studied veneer of old-fashioned American values.

Jim Carrey, a fearless physical comedian whose exaggerated facial tics seem to reflect a twisted soul, is perhaps the perfect choice to play Steven, who, after a near-death experience, leaps out of the closet and lives the life he has imagined but never dared to pursue. Relocating to Florida, he accessorizes, grabbing two pugs, a boyfriend and enough credit-card debt to land him in a federal penitentiary.

Steven, it turns out, is a natural con man: Highly intelligent, casually charming and shameless enough to back up even the most outrageous lies – he passes himself off as a lawyer, and later a financial whiz – he is either a pathological liar, a sociopath or both. And yet he is neither hard-hearted nor cruel. Self-absorbed, yes, but Steven is strangely loyal to the few he invites behind the curtain of his assumed personality – among them, his prison sweetheart, Phillip Morris.

How much he allows Phillip to see is debatable. Steven is a romantic, but there is a void inside him that no number of fast cars, designer suits and expensive watches will ever fill. No bank account is big enough. His passion for Phillip and his instinct to protect him is real. But even the unconditional love he has sought since childhood isn’t sufficient to keep him honest.

I Love You Phillip Morris is inspired by the real-life exploits of legendary con artist Steven Jay Russell, nicknamed “Houdini” for his uncanny talent for breaking out of prison – always in the name of love, we’re told – and now serving a 144-year sentence in the maximum-security ward of a prison near Dallas. The real Phillip Morris, who lives alone in his native Arkansas, portrays his former flame far less charitably than do screenwriters John Requa and Glenn Ficara, who treat his serial betrayals as brazen goofs.

And so they are, on some level, but not to people like Phillip, played here as the proverbial straight man by Ewan McGregor. Phillip, who first landed in jail for an overdue car rental, is an innocent. Gently unassuming, eager to find a friend in a sea of hardened inmates, he takes Steven at face value and ultimately finds himself an unwitting accomplice in a series of outrageous scams. Pained, he flashes his boyish grin – McGregor’s specialty – and bears it.

As he has since graduating from In Living Color in 1994, Carrey owns the screen whenever he’s on it, and he is a gifted dramatic actor. As Steven, an enigmatic con man reminiscent of Matt Damon’s bogus corporate whistleblower in last year’s The Informant!, his manic eccentricities and transparent disingenuousness lend themselves to broad but effective comedy. But in Steven’s quieter moments, when the character requires a certain gravitas, it’s hard to separate the leering prankster from his compassionate alter ego.

Perhaps that’s the point. Steven is always “on” – even his closest confidantes can’t seem to reconcile his better nature, and his genius, with his failings and lies. What’s to be believed? Whether you see his as a problematic love story or the improbable ballad of a charismatic loner undone by greed, he is fascinating at every step, true or false.

I Love You Phillip Morris opens Friday at the AMC Loews Metreon. For tickets and showtimes, click here.