DS was a completely original idea thought up by Dan Curtis and fleshed out by Art Wallace.
Not so. Wallace based much of the original idea for DS on his teleplay for The House, which is about a reclusive woman named Caroline, whose husband had been missing for years, and her daughter Elizabeth. (Wallace simply switched the characters' names for DS - and changed Caroline to Carolyn.
) I've only read bits and pieces about it, though, so I'm not sure if Caroline also believed she'd murdered her husband. But I suppose we'll find out at the Fest...