Agnes is disappointed when she discovers she is not invited to Maria's hen party because she is too old, so she and Winnie decide to crash the event, but end up in the wrong venue. She invites Maria's mother round for dinner and is so nervous about impressing her that she gets drunk and the evening descends into chaos.

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.

Newlyweds Dermot and Maria argue over whether they should buy their own home. Meanwhile, Mrs Brown tries to make Grandad happy by secretly staging a funeral for him, but the plans go awry when she mistakes two Mormons - who have been stealing Father Quinn's parishioners - for the men who are supposed to be delivering the coffin.

Agnes Brown’s son, Dermot, and his new wife, Maria, have a baby on the way, and they are desperate for a place of their own, as the smash-hit comedy written by and starring Brendan O’Carroll continues. The newlyweds just can’t afford to move out, but Mrs Brown has a plan to help her son. Loving mother that she is, Agnes has promised the couple the money from Grandad’s life insurance policy payout for a deposit for their own home. There’s just one minor hitch – Grandad is not dead. Caught between a suspicious insurance company and her God-fearing son, Trevor, Agnes has to resort to desperate measures to keep Grandad out of sight and her dream alive.

A secretive phone call from a solicitor to Mrs Brown leaves her children suspecting one of them may be adopted, while Father Quinn returns from rehab and asks Agnes to help out at his annual garden party - although as she proceeds to drive him crazy with a smartphone, his recovery may be short-lived. Meanwhile, Cathy receives a blast from the past, Rory and Dino have a bust-up, and Mark and Betty deliver bad news - they are leaving for Australia right away.