We all knew there were three sisters. We were all wrong...

Three sisters (doctor Piret, interior designer Mari and psychologist Kertu) discover that they have one more sister. Shocking news challenges family relationships and forces them to ask why their mother has hidden her first child's existence. When the fourth sister decides to come and visit her mother and sisters in Haapsalu, events that nobody could expect started happening. Is blood thicker than water and the stranger becomes theirs?