Mystery Man on Film wrote:

There is a link now available to download the 125-page transcript (in the form of a .pdf document) of the original 1978 story conference between Steven Spielberg, George Lucas, and Lawrence Kasdan for a little film called Raiders of the Lost Ark.

Mystery Man on Film wrote:

Interestingly, the discussion about Marion was hardly as thorough as the one about Indy. For a while, they weren't sure what kind of girl to have as a counterpart to Indy. Lucas had first described the love interest as a blonde double-crossing German agent, which they ended up using in Last Crusade. Spielberg said, “She should have hair like Veronica Lake. You only see one eye at a time.”

There was talk about a big name professor who taught Indy everything he knew. Then there was the idea about this German girl, and for the sake of expediency, Kasdan suggested that Indy instead have an affair with the mentor’s daughter, which they loved. And then Lucas and Spielberg were off and running with ideas about how’s she’s been left in Peru and has this bar and is trying to get money together to get back to the States and loves (and resents) Indy to no end. In fact, Kasdan said he wanted Indy and this girl to already have a history when they meet because, “I like it if they already had a relationship at one point. Because then you don’t have to build it.” Hehehe…

Then the discussion turned to how old Marion and Indy were at the time of the affair:

George — I was thinking that this old guy could have been his mentor. He could have known this little girl when she was just a kid. Had an affair with her when she was eleven.

Lawrence — And he was forty-two.

George — He hasn't seen her in twelve years. Now she's twenty-two. It's a real strange relationship.

Steven — She had better be older than twenty-two.

George — He's thirty-five, and he knew her ten years ago when he was twenty-five and she was only twelve. It would be amusing to make her slightly young at the time.

Steven — And promiscuous. She came onto him.

George — Fifteen is right on the edge. I know it's an outrageous idea, but it is interesting. Once she's sixteen or seventeen it's not interesting anymore. But if she was fifteen and he was twenty-five and they actually had an affair the last time they met. And she was madly in love with him and he...

Steven — She has pictures of him.

And now consider the dialogue of that scene in the film:

INDY: I never meant to hurt you.
MARION: I was a child! I was in love.
INDY: You knew what you were doing.
MARION: It was wrong. You knew it.
INDY: Look, I did what I did. I don't expect you to be happy about it. But maybe we can do each other some good.
MARION: Why start now?
INDY: Shut up and listen for a second. I want that piece your father had. I've got money.
MARION: How much?