Are You...? - S7-E1
Factual error: During the walk-through of the crime scene, there is a small remnant of plastic sheeting between Travis' toes. Given the entire church was consumed by flames, or more importantly, the body and foot from which the plastic is pulled are badly burnt, it's highly improbable that the plastic sheeting would still be present. At least not in the form that is shown, but rather more like a globe of melted plastic on or into the body or table. Similarly, the feet wouldn't be 'wet' or glossy with blood. (00:15:22)
Answer: No, Harry is not the real father. While he did have an affair with Dexter's biological mother (Laura Moser), this was when she was his C.I. Dexter was already born at that point.