StineandTeit,youraverageurbanmiddle-classartistsandintellectuals,leaveCopenhagenforthewildsofneighbouringSweden’sforest.Soon,theyfindoutthatsomethingisstrangethere–mostdisturbingly–whentheirsonNemosuddenlythinkshismotherisn’treallyhismotheranymore.ItbecomesclearonceStineandTeitdiscoverthattheyhaveneighbourswholookexactlylikethem–mirrorimagesmadefleshandblood.
Thesubjectofreflectionsanddoublesisintroducedinthefilm’sfirstshot:aviewofalakelandscapeturned90°sothatthewater’ssurfacerunsverticallythroughtheimage’scentre.Onlyoncetheshotgetstiltedisitrevealedwhichsidemirrorswhich.Later,amotherandchildarereflectedinaglassdoor.
However,thisisnotyourdoppelgangerthrillerofthegothicvariety.Notethetitle:inphysics,superpositionmeans(perMerriam-Webster)"thecombinationoftwodistinctphysicalphenomenaofthesametype(suchasspinorwavelength)sothattheycoexistaspartofthesameevent".Thisismoreametaphysicalmeditationtowardstherealisationthatnoneofusiseveralone,butalsoneverunique.