Estella Margaret Montiel is a dedicated governess for House Bertha. However, she is currently facing more pressing matters than math or grammar. She knows her pupils' half-brother, Duke Diego Bertha, plans to kill everyone in his family! Determined to protect her students from a tragic fate, she sets out to reform the charming yet dangerous duke. Can her resolve and guidance truly transform the devilish Diego and teach him the value of family? Or will her class be dismissed much too early?