Based on the non-fiction book by Steve McVicker, "I Love You Phillip Morris" is sure to attract curiosity-seekers for the simple fact that it is a gay love story starring Jim Carrey (2009's "A Christmas Carol") and Ewan McGregor (2010's "The Ghost Writer"). That the same-sex relationship is treated nonchalantly, like any more conventional Hollywood romance, is appreciated, but that is roughly where the praise must unfortunately end. Written and directed by Glenn Ficarra and John Requa, making their helming debuts, the film stinks of artificiality even as it repeatedly purports being based on true events. Too jokey to be taken seriously and too much of a downer to work as the crime caper it wants to be, "I Love You Phillip Morris" is so tonally schizophrenic, underdeveloped, and subjectively streamlined that it never rises above its own terminal blandness.

After narrowly surviving a nasty car accident, married ex-cop Steven Russell (Jim Carrey) has a life-changing epiphany. No longer able to hide who he is, he comes out to understanding wife Debbie (Leslie Mann), splits from his family, and takes up with boyfriend Jimmy (Rodrigo Santoro) in Miami Beach. Being gay and fabulous comes with a literal price, however, and soon Steven is committing every type of fraud under the sun to keep up with his expensive new lifestyle. His actions eventually catch up with him, and it is in prison that he meets and almost instantly falls in love with adorable fellow inmate Phillip Morris (Ewan McGregor). When their sentences are over, they move in together and prepare for a long, happy life. For Steven, however, once a conman, always a conman, as he proceeds to steal from his new employer and consequently put his relationship with Phillip in jeopardy. With more jail time imminent—and destined to be much longer this time—is there any chance for Steven and Phillip to still work things out and walk away into the sunset?

"I Love You Phillip Morris" opens okay, setting up Steven's public and private lives before a near-death experience urges him to meld the two. Despite being devoutly religious, wife Debbie is refreshingly written as a caring, open-minded woman. The trouble is that she's so likable the viewer can't help but feel sorry for her once Steven admits his sexuality and tosses her and their young daughter aside for a shallow, exorbitant and increasingly criminal existence in Miami. Flashbacks to Steven's childhood as an adopted kid, and his unsuccessful attempt to reconnect with his birth mother as an adult, are pretty flimsy excuses for his illegal activities and don't really add up to anything. Once in prison, the initial scenes between him and Phillip show promise, less because of the scattershot screenplay and more because Jim Carrey and Ewan McGregor share a sweet, rather sexy chemistry. We want to see how their relationship unfolds and we root for them to stay together until Phillip, too, is mishandled, resorting to the thankless role of a houseboy who hangs around and does little but answer to his man. Meanwhile, Steven picks up where he left off, lying and thieving thousands upon thousands of dollars for no good reason. What is his purpose in doing this? The movie doesn't seem to know and chooses not to provide an answer.

Jim Carrey adopts a southern drawl but eases up on his signature overcaffeination as Steven Russell. He's still playing quite a character, but it is an unusually restrained performance. What Carrey is not able to do is burrow deeper beneath the surface of Steven's charade; even when he's being serious there's always the possibility that he's pulling the wool over one's eyes in another con. It's a frustrating protagonist to have to follow, and he comes with none of the pathos of, for example, Leonardo DiCaprio's similar character in 2002's "Catch Me If You Can." The fact that his only relationship with his ex-wife and daughter is over the phone and through monetary gifts that he's stolen makes him all the more callous. As Phillip Morris, Ewan McGregor is gentle and endearing, but a backseat participant by the end. He deserves better than Steven.

Repetitive and unconvincing, "I Love You Phillip Morris" is stuck within the constraints of its factual story, yet never truly proves that it understands its conniving human subject. The film runs in circles as Steven swindles, gets caught, finds a way to escape jail, and then repeats the process over. Writer-directors Glenn Ficarra and John Requa try to shove in a spot of soul-searching after Phillip breaks up with him—near the end, Steven says in voiceover, "In the process I lost track of who I was"—but his actions following this statement prove that he hasn't learned anything and is destined to constantly resort back to his old ways. A twist near the end is as unforgivable as its irresponsible abuse of the AIDS virus as a plot device. There are plenty of quirky, funny, sincere love stories to be told between two men—indeed, there already have been a few, like 1999's wonderful "Trick"—but "I Love You Phillip Morris" isn't one of them. If Phillip knows what's good for him, he'll drop Steven fast and find a guy whose words of affections to him won't always have him questioning whether they're genuine or just another ruse in his bag of tricks.