The structure of playwright Lois Brown’s Sex, the Rules of is not simple. It follows a twisty path through truth and fantasy, and while this means it requires close attention from the audience, it also proves to be an excellent representation of the complexity of real life. The show is about a family that has spent years dealing—or not dealing—with the drowning death of a child. Sex becomes many things: an outlet for guilt, a weapon used to hold others at arm’s length and a way to experience some sort of tenderness. Aiden Flynn as the 50-something father is particularly riveting, and his father-son talk with Mark O’Brien who plays his needy and mixed-up son is hilarious. Marthe Bernard is an appropriately disturbing mix of child-like and sexy and Ruth Lawrence nails it as the strident yet fragile grieving mother. While you may not like any of the characters, you will come to understand them, and that makes for engrossing theatre.