Catherine Warner and Simon Nelson are best friends: total opposites, always together, and both unlucky in love. Cath is scatterbrained, messy, and–since she had her heart broken a few years back–emotionally closed off. Si is impossibly tidy, bitchy, and desperate for a man of his own. They live in London’s West Hampstead along with their lifelong friends, Josh and Lucy, who are happily married with a devil-spawn child and a terrifying Swedish nanny, Ingrid.