InsomniatellsthestoryofsuccessfulcareerwomanEmmaAverill,whofearssheislosinghermindaftersufferingfromsleepdeprivationtwoweeksbeforeturning40.Hermotherhadasimilarexperienceatthesameage,sufferingaviolentpsychoticbreakdownonthenightofher40thbirthday.Butevenassherelivestheexperienceofhermother,Averillbelievesotherforcesmaybeatwork.Hermotherishospitalizedwithasuddeninjury,herestrangedsisterreturnswithoutwarning,andshefeelsasifsheisbeingwatched.Onlybyinvestigatingthetruthofherpainfulpast,canshefindtheanswerstoherpresent.