Footage he hoped would reveal signs of paranormal activity in his Tasmania, Australia, house instead showed his two loved ones kissing and then having intercourse.
He confronted his 28-year-old lover - who'd lived with him for 11 years and is the mother of his young child - but she played down the October 2012 incident.
However, his son confessed to having sex with her three times in the preceding days.
And in the following weeks, it emerged they went on to have sex several times in a hotel room.
The man called cops. Officers questioned his partner, who admitted to having sex with the boy and knowing he was 16.
She claimed to think the age of consent was 16, when it is actually 17, and said she was "ashamed and embarrassed" by her conduct.
The woman, who cannot be named for legal reasons, pleaded guilty to underage sex at the state's Supreme Court on Monday.
The Hobart Mercury reports she will be sentenced next week. .....Courtesy of Daily News