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. However, her heart-to-heart with Maria only succeeds in making the dispute worse.

Agnes Brown is concerned that her family are keeping too many secrets. Her daughter Cathy will not let her meet her new boyfriend, while her elder son Mark refuses to reveal why his feisty wife Betty has thrown him out. When Betty and Mrs Brown meet to discuss Mark's problem, they unsurprisingly come to blows. Can Betty and Mark reconcile in spite of Agnes' interference?

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. On top of this, Mrs Brown's close friend and neighbour Winnie is distraught. Her husband Jacko has been rushed to hospital.

Agnes Brown and her friend Winnie gatecrash Dermot's fiancée Maria's hen party, but realise that they have the wrong venue. Later, having invited Maria's snooty mother Mrs Nicholson to dinner, a nervous Agnes shores up her confidence with alcohol, but chaos ensues as the evening proceeds.

With his wedding only days away and tensions running high, Dermot suffers some pre-wedding jitters and takes refuge in a cupboard. Will Agnes be able to coax her son out in time for his nuptials? Meanwhile, Cathy gives her mother a book on homosexuality, leading Agnes to wonder who in her family is gay.

Agnes Brown thinks everyone has gone mad; Father Quinn is losing his faith as fast as he loses parishioners, newlyweds Dermot and Maria won't stop fighting, and Grandad has decided he'd like to witness his own funeral. The Browns decide to make Grandad happy by secretly staging his funeral, but their plans start to go awry when Mrs Brown mistakes two Mormons for the men who are supposed to be delivering Grandad's coffin.