Meet “Late Show” assistant Stephanie Birkitt — the woman unknowingly at the center of the extortion case against David Letterman and the former girlfriend of “48 Hours” Robert “Joe” Halderman, the man accused of doing the actual blackmailing. Confused? Good. Radar Online says

Stephanie Birkitt met Halderman at CBS about 15 years ago. At the time, Halderman was in one of his two past marriages, and Halderman did not have a relationship with Birkitt.

Birkitt later got a job on Letterman’s show and has worked there for more than a decade, often appearing on air.

Our source [say] that Birkitt and Letterman slept together for a period of time before he married his girlfriend Regina had their son Harry. After Halderman divorced, the source says he got involved with Stephanie and she lived with him in Connecticut.

The source says Birkitt told Halderman that she had had sex with Letterman.

So it seems that while they were living together (and without her consent), Halderman went through Birkitt’s personal effects for proof of hers and Letterman’s affair to use to blackmail the talk show host, including

Copies of parts of a diary and correspondence belonging to Birkitt, [along with] documents, letters, emails and photos.

Jesus, I didn’t know anyone other than 8th grade girls kept actual diaries. What a stupid idea. I guess you never know when all your puffy hearts and triple-underlined “Mrs. Stephanie Lettermans” will come back to bite you in the ass.

Olivia Wilde arriving to The Late Show: