Dermot's pre-marriage nerves get the better of him and he locks himself away in a cupboard, so it is up to Agnes, Fr Quinn and best man Buster to try to calm him down. Meanwhile, Rory tells his mother he is gay.

All over Dublin, mothers are excitedly looking forward to seeing their loved ones return home for Christmas. But Agnes Brown is depressed. Her son Trevor is on the missions in Canada, and can't possibly afford to make it back. With Maria's posh mum Hillary pressing the newlyweds to spend Christmas at her place, Agnes decides to compete for their love by providing an even more lavish Christmas celebration than Hillary's - even if Buster is having trouble delivering the turkey.

Baby fever hits the Brown household as a pregnant Maria prepares for motherhood, and Agnes is keen to give her new daughter-in-law her unique brand of advice about raising children. Maria is grateful when Agnes offers to look after the robot baby she has brought home from her pre-natal class, but it turns out that Mrs Brown's babysitting techniques are not exactly orthodox. And Maria has some exciting news for the Brown family.

When Agnes's family start making comments about her weight, she decides to go on a diet, and quickly discovers just how difficult it is to overcome her craving for fish and chips. Cathy brings her new, older man home. He is a psychiatrist, and seems much more interested in Agnes than he does Cathy. Meanwhile, Rory has a professional dilemma when he discovers some illegal drugs at work.

There is bickering aplenty in the Brown household, as Rory and Dino are on the rocks and Agnes and Betty rub each other up the wrong way. With Maria about to give birth, Cathy convinces Agnes to build bridges and invite Maria's mother Hillary out for dinner. However, the night comes to an abrupt end when Maria goes into labour. Can the family get Maria to the hospital in time?