After their flight from Finland is delayed, strangers Josh and Fola get drunk and sleep together, unbeknownst to their partners back home. When Josh gets home the next day, he is shocked to discover that Fola is his new neighbour

After Josh and Fola are reunited with their respective partners, things get complicated when Fola's husband Zack invites his new neighbours to their house-warming party. Josh's girlfriend Esther accepts, leaving Josh stressed.

After the awkwardness of the house-warming party, Fola confronts Zack over their non-existent sex life. Fola heads over to see Josh, each realising that there might be more to their relationship than just a one-night stand.

After another aborted attempt at sex with Fola, Zack impulsively buys some Viagra at the chemists and bumps into Esther. After their prescriptions get mixed up, Zack is embarrassed to realise that Esther will discover what he bought.

Zack gets his prescription back from Esther and their friendship blossoms, each unaware that they are being cheated on by their partners. Meanwhile, Josh discusses the situation with his sister Nina, who advises him to end it with Fola.

Josh visits Fola, intent on ending things, but despite their best intentions, they end up sleeping together for a second time. Meanwhile, Zack leaves work early to surprise Fola with his Viagra, only to overhear Fola and Josh having sex.

Zack tries to process what he witnessed the night before. Josh and Fola try to agree the rules for their clandestine relationship, only for Josh to unknowingly break them straight away. Esther is planning her school reunion.

Esther's school reunion goes disastrously wrong as she is forced to face some difficult home-truths about her life and the decisions she's made. After an encounter with an ex-boyfriend Fola turns to Josh for help and moral support.

Still reeling from the events at her school reunion, Esther bares her soul to her boss, Karen. Realising that she needs to make changes to her life Esther makes a decision about her relationship with Josh.

Josh stresses preparing a family meal for his Grandad's 80th birthday, and to complicate matters he has to ask Zack and Fola for help. Sensing an opportunity, Zack conspires to get Fola and Josh to spend some time alone together.

Josh gets into a heated argument with his Dad at the family meal. Meanwhile across the road Zack decides that it's time to confront Fola and tell her that he knows about her and Josh.

After discovering a family secret, Josh decides to make an announcement about his and Esther's future. Reeling from her argument with Zack, Fola realises that perhaps Josh isn't as committed to her as she thought.

Still trying to patch-up his marriage with Fola, Zack goes to pick his Dad up from the airport, only to receive some devastating news. Josh and Esther bring forward their wedding plans and begin to organise their joint stag and hen do.

Josh bumps into Zack and learns that his father has died, but as Fola has temporarily moved out she doesn't know. As Zack heads off to the funeral, Josh makes a decision and calls Fola. Will she make it to the funeral in time?

While out on their joint stag and hen do, Esther discovers a secret that threatens her relationship and Josh is forced to make a confession. After bonding at the funeral, Zack and Fola's relationship seems to be back on track.

As Josh tries to salvage his relationship with Esther, Fola and Zack rekindle their sexual attraction in the most unusual way. To complicate matters further, the stag and hen party turns up at the same pub that Zack and Fola are at.

Caught between the two women that he loves, Josh asks Nina for some sisterly advice. Realising that he can't keep lying to himself for ever, Josh decides it's time to tell Fola how he really feels about her.

As the events of the party spiral out of control both Josh and Fola risk their relationships for each other, only for Josh to realise that Fola might not have been entirely honest with him about her relationship with Zack.