There's Something About Mary Lynn Obsession: Dark Desires : Season 3 Episode 10

Single mom Mary Lynn falls for divorcee Edmonds, but early on she realizes there is something not quite right about his 10 year old son, Tennent. What she doesn't know is that Tennent doesn't just like Mary Lynn, he wants to become her. It's the beginning of a terrifying 22 year obsession that will devastate both families.