"Years ago, a deceased redheaded pretender made a pact with the devil. When she passed on, most believed any secrets she had went with her to the grave. Won't everyone be surprised when they find out not only is this not true, but she left behind a whole lot more than secrets."
You could read the 'not only is this not true' part as referring to her not actually being dead. That's how I take it anyway given Secret #5.
If Madelyn never died--or if she's been resurrected--then technically Scott and Jean are still involved in an 'affair,' since he never divorced Madelyn.
You've also got Sinister Secret #9, which makes reference to a 'non-couple couple' that's been apart for a long time, with fireworks expected to ensue when they meet up again and the word...Inferno.
I'm definitely thinking all signs point to Madelyne!