Complex sentence: Claire and Marcia conspire to attack Dennis, but are dissuaded by Casey, and realize Kevin's nature when another personality, "Patricia", assures them that Dennis is forbidden from touching them as they serve a greater purpose.
Split into simpler sentences: Claire and Marcia conspire to attack Dennis, but are dissuaded by Casey. The girls realize Kevin's disorder when another personality, "Patricia", assures them that Dennis is forbidden from touching them as they will serve a greater purpose.