Roy Scheider Episode Question

SPOILERS

I watched last night with Roy Sheider as the serial killer and how they were trying to track down all the bodies of the women he murdered. While going through old pictures one is recognized to be the detectives mother. He shows the picture to his brother who says "oh yeah, that's uncle Marc. He used to come around a lot when dad was in the service". He shows the picture to his mom and she says the same thing until the detective pretty much tells her the jig is up. She breaks down crying and doesn't say exactly but says "yes I know who he IS (that he's the convicted serial killer) but what I did not understand was if they were suggesting that he be the father of the detective through an affair that they had. Is THAT what they're saying? If so; did Sheiders character know this?