Orphaned siblings Tristan, Katinka, Kirk, and Petra have formed a new family after being "hired as children" by their former nanny Nelly and her partner Brian. Settled into their new home in Martinsbay, they eagerly await their best Christmas yet — until a strict child services officer arrives with troubling news: their grandparents are demanding custody. With the law on the grandparents' side, the four siblings hatch a series of outrageous schemes to stay together with Nelly and Brian in their newfound family.