Two families - Josh, Hannah and their daughter Lily; and Dan, Sasha and their daughter September - have shared life and laughs since their children were babies. It is a perfect, close-knit world where friends trust each other implicitly - until one of them drops a bombshell that changes their lives forever. Best friends tell you everything: about their kitchen renovation; about their little girl's schooling. How one of them is leaving the other for a young model. Best friends don't tell lies. They don't take up residence on your couch for weeks. They don't call lawyers. They don't make you choose sides. Best friends don't keep secrets about their past. They don't put you in danger. Best friends don't always stay best friends...