It was just a chance encounter on a downtown New York City street, but she was instantly enamored.

"I've seen you on TV. You're so cute," the woman who would later accuse Greg Kelly of rape said, according to a law enforcement source.

The brunette crossed paths with the handsome "Good Day New York" TV host two days before the alleged attack.

What followed was about 48 hours of marathon text-messaging ahead of their Saturday-night date at the South Street Seaport.

"The texts were explicit," the source said. "They were sexual."

Kelly and the 29-year-old paralegal, an aspiring model and actress whose name is being withheld by the New York Post, also spoke by phone and exchanged emails before meeting up, the source said.

On the night of their date, the woman's boyfriend was at home, so she concocted an excuse to get out on her own.

"She lied to the boyfriend to meet Greg that night. She said, 'I'm going out with a girlfriend,'" the source said.

They ordered drinks at a bar, running up a tab that another source described as "laughably low" -- and then headed to the woman's lower-Manhattan law firm.

They had sex there, right in her boss's office, the source said.

If the woman was upset about the randy romp, she gave no clue in follow-up messages to Kelly, the son of Police Commissioner Ray Kelly, the source said.

"They continued to text," the source said. "Part of it was about arranging another date."

In total, there were 17 text messages between the two.

But the woman, whose brother is an NYPD sergeant assigned to the crime-scene unit, insisted she was sexually assaulted by Greg Kelly and claims that she had so much to drink that she was incapable of rejecting his advances.

The source added that investigators from the district attorney's office are aggressively looking into every possible piece of corroborating evidence, including videotape from the woman's office building and witnesses who might have seen the couple coming in or leaving.

The woman told prosecutors that Kelly, a single former US Marine, got her pregnant and that she underwent an abortion.

The source believes the case will hinge on the accuser's motivation, asking, "What drives someone who's making a delayed report?" The accuser did not come forward until last Tuesday, three months after the affair.

The NYPD immediately handed the investigation over to the Manhattan district attorney because of the inherent conflict of interest.

Greg Kelly, meanwhile, was keeping a low profile and has not been seen in public since Thursday, when he took an indefinite leave of absence from "Good Day New York" on WNYW. The TV station is owned by News Corp., the parent company of the New York Post and NewsCore.

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