Cassandra Serene Sandoval is not a Miss-Goody-Two-Shoes as everyone expected her to be. Hindi siya ang perfect model daughter gaya ng iba. She's different. She's a playgirl and an evil. At dahil sa ugaling niyang matapang at walang inuurungan, Her friends offered her a deal for an exchange of Trip to Paris that she have always dream off. Ang deal ay ang makasama sa iisang bahay ang pinaka-hate niyang tao sa mundo for 100 days! Paano kung mapasubo siya sa sarili niyang laro lalo na't involved ang pinakaiingat ingatan ng kakambal niya? Will she lose the bet just to get rid of the person she hates the most and see her brother doomed? or fight for the bet and get everything back to normal?