After Catherine Walcott's father dies, she discovers that he had a second secret family, including another daughter named Catherine Walcott.

Cathy and Cat search for their father's will as their mothers argue over which family their dead dad loved most.

Cathy is put on compassionate leave from work and asked to attend grief counselling; Cat wants to be Cathy's maid of honour and offers to take care of the wedding dress.

Cathy boxes up her father's things in preparation for selling the house; Cat and Marilyn go overboard taking mementos; Cathy teaches Cat how to ride a bike; Marcus visits the dump.

With her mother refusing to go, Cathy's bachelorette party invitees are Auntie Dawn, Marilyn, Cat and an old school friend, but it doesn't turn out to be the classy, edifying affair the bride-to-be wanted.

Having finally come to terms with the fact they're sisters, Cathy and Cat are shocked by the news that they also have a brother, Callum, and that Cathy just snogged him.