Fiona decides to celebrate her husband's 50th birthday by organising a camping weekend with friends Kerry and Adam. However, her perfectly organised trip is thrown drastically off course by the arrival of the recently separated Tom and his uninhibited new partner Fay.

As the group settles uneasily into the weekend, a visit to the beach is beset by a detour to A&E with Robin and Fiona's mollycoddled son, Archie. Meanwhile, Tom and Fay get up to no good in the changing room of a vintage shop, and there is an awkward encounter involving an antique engagement ring. Plus, Kerry keeps reminding everyone that Adam is an alcoholic.

Fi has planned for the group to visit Monkey World, and is predictably furious when Tom and Fay give Robin the gift of an impromptu fishing trip. As Fi sticks to her guns and goes to see the primates, Robin, Adam, Kerry and the kids take to the seas, with disastrous results. Meanwhile, Tom and Fay try to score some drugs.

Robin makes an attempt to reignite his and Fi's sex life for his birthday, while Tom receives some bad news regarding his estranged wife.

To celebrate Robin's birthday, the gang put on a talent show, but the festivities are interrupted when Adam and Kerry clash over his flirtation with Fay. Plus, some experimentation with Fay's drug stash sees everybody's deepest desires emerge.

As the holiday from hell draws to a close, Adam falls off the wagon and Robin's party descends into substance abuse, blazing rows and awkward sexual encounters.