After their flight from Finland is delayed, strangers Josh and Fola end up getting drunk and sleeping 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 offers his new neighbours an invitation to their house-warming party. Josh's girlfriend Esther happily accepts, leaving Josh stressed.

After the awkwardness of the house-warming party, Fola confronts Zack over their nonexistent 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 manages to get his prescription back from Esther, and their friendship blossoms, each unaware that they are being cheated on by their partners; Josh discusses the situation with his sister Nina, who advises him to end it with Fola.

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