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.

Agnes and the family set up a fake funeral for Grandad, after he decides that he would like to hear what people will say about him after he dies.

With his wedding only days away and tensions running high, Dermot suffers some pre-wedding jitters and takes refuge in a cupboard. Cathy gives her mother a book on homosexuality, leading Agnes to wonder who in her family is gay.

It's the week of Dermot's fiancee Maria Nicholson's hen party, and Agnes Brown and her friend Winnie are excited about going... until daughter Cathy tells them they are not invited because they are too old. Undeterred, Mrs Brown decides she will crash the event and show the girls that she and Winnie are not too old to party. All she has to do is find out where the party is being held. Agnes thinks her luck is in when son Dermot tells her that the girls are meeting at local pub Foleys. But when Agnes bursts into the pub in full hen-party attire, it becomes clear that Dermot may have misinformed her.

That night, Agnes Brown mistakenly invites Maria's snooty mother Mrs Nicholson to dinner. Finding out that Mrs Nicholson is so sophisticated that she has two toilets in her house, Agnes has one fitted in an understairs cupboard in order to impress her guest. Despite this, and despite drafting in Rory's cordon bleu friend Dino to cook dinner, on the night Mrs Brown is incredibly nervous and turns to drink. With Mrs Brown increasingly desperate to delight Mrs Nicholson, the evening descends into chaos as the drink takes hold, the aftermath of Agnes's hen party mistake plays out, and Grandad decides to go to the toilet in the wrong cupboard.

With Dermot and Maria's wedding just weeks away, the Brown household is in crisis.

Agnes Brown's son Dermot wants to ask his childhood friend Buster to be best man. But Agnes has set her heart on Mark Brown, her eldest son, being Dermot's best man. And Buster is a crook, of whom both the strong-willed Maria and Mrs Brown strongly disapprove.

On top of this, Mrs Brown's close friend and neighbour Winnie is distraught. Her husband Jacko has been rushed to hospital and cannot possibly afford to pay for the operation he urgently needs. And, needing cash for his wedding, Dermot has allowed himself to get embroiled in one of Buster's stupid- and dodgy - moneymaking scams.

It's time for Mrs Brown to exercise all her diplomatic skills, starting with 'accidentally' letting Maria know all about Dermot's best man decision.

Agnes Brown is concerned that her family are keeping too many secrets. Her daughter Cathy won't let her meet her new boyfriend. Her elder son Mark won't reveal why his feisty wife Betty has thrown him out. And her younger son Dermot has lied to his fiancee Maria Nicholson's well-to-do parents about the status of his job.

Agnes Brown has family troubles to contend with: her son Dermot has fallen out with Maria Nicholson, his long-term girlfriend, and Grandad is feeling poorly.

After a sleepless night, Mrs Brown decides to try to sort out Dermot and Maria's problem by giving Maria the benefit of her advice. But her heart-to-heart with Maria only succeeds in making the dispute worse. So Mrs Brown's daughter Cathy intervenes. She's a psychology student, and offers Dermot and Maria a counselling session. A dismayed Mrs Brown can't help interfering, and the session quickly descends into a blazing row between her and Cathy... with an effect on Dermot and Maria that not even Agnes Brown could have predicted.

Meanwhile, Grandad ends up in hospital when Dr Flynn's attempt to read his temperature goes dramatically wrong. And Cathy reveals the electrifying secret of how she keeps dodgy men at bay.