The kidnapping, false identity and potential double-homicide case that captured the nation's attention during the summer of 2008 is back in the news – this time, starring a TV favorite.

Eric McCormack portrays the alternately charming and alarming faux aristocrat in the Lifetime TV movie Who Is Clark Rockefeller?, premiering Saturday at 9 p.m. ET/PT. It revives the drama of those hot-weather months, when Rockefeller, who not only trumped up his name but his credentials, led authorities on a tense manhunt along the East Coast to find him and his 7-year-old daughter Reigh, known to her parents as Snooks.

"He loved that baby," the Will & Grace Emmy winner, 46, tells PEOPLE by way of explaining Rockefeller's motivation – as well as the desperate father's life-altering decision to shed his fancy veneer and assume a humble, new life with his child. "When you become a father," says McCormack, himself the parent of a 7-year-old, "everything changes."

Meanwhile, only last week the "real" fake Rockefeller, a German national identified by the FBI as Christian Karl Gerhartsreiter, was denied a new trial in his kidnapping case, reports the Boston Herald. Currently serving a four- to five-year state prison term for abducting his child and assaulting her bodyguard, Rockefeller (who has also been identified as a person of interest in a double-homicide that took place during the mid-'80s in California) is expected to be released in 2012.

"I don't think he was that crazy," says McCormack, who likens Rockefeller to "the ultimate Method Actor," believing without a doubt he was the character he created. "He was driven. But, like Hamlet, at some point, he crossed the line. He looked in the mirror and he saw Clark Rockefeller."

Mimicking a Fake

To capture the cadence of Rockefeller's speech, McCormack, who has never met Rockefeller, absorbed NBC's Natalie Morales's jailhouse interview. He also pored over a Vanity Fair profile, "The Man in the Rockefeller Suit."

And while the TV movie doesn't entirely answer the question posed by its title – or why Rockefeller's Harvard-trained corporate consultant wife Sandra Boss (played by ER's Sherry Stringfield) didn't see through the mirage earlier in their 12-year marriage – it does offer juicy insight into their relationship, such as the final showdown between Boss and Rockefeller, when she pays him off to end the marriage and any claim on their child.

The dialogue in the scene, says McCormack, was based on public record.

Murder Mystery

The script also brings up the case of Christopher Chichester, a mysterious young man who in 1985 left San Marino, Calif., in a pick-up truck belonging to his landlords, a married couple whose skeletal remains were evenutally uncovered in 1994. In 1988, the truck turned up in tony Greenwich, Conn., where someone named Christopher Crowe tried to sell it. Police said Chichester and Crowe were one and the same person – but then, he disappeared.

While the public waits to see if the cold case in San Marino will be reopened, the actor who plays Clark Rockefeller says only, "Possibly in 1985 he did something nefarious." Still, McCormack admits, Rockefeller is "a sociopath, for sure, and twisted."

As for Rockefeller's ex-wife, Reigh's mother, who has granted no interviews in the matter? She exercised what McCormack considers "a chosen ignorance." After all, the actor suggests, "It takes two to tango, and she danced."

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