The doctor's practice, first introduced in No White Coat and again in Love on my List, is expanding. He finds himself buckling under the strain of an increased workload and the demands of his exuberant twins. His wife, Sylvia, persuades him to take a much-needed break and he realises that it is time to find an assistant. Into this busy environment arrives the doctor's alluring cousin Caroline. On a study visit from the US, she invites herself to stay for six months - a situation which causes much chaos and hilarity.