For Elizabeth , self is not I , it’s we . From a very early age , Elizabeth has suffered from Dissociative Identity Disorder . She doesn’t like her own name and prefers to be referred to as Elise – the default alter ego . Then there is Lillie – the hard-headed & quick-thinking 18 year old who refers to herself as the resident crisis-manager of the ” tree- house” . The tree- house is the imaginary ” house ” where Elise’s alters convene and discuss about the tough situations and decide what needs to be done and who is the best person to take over the body at that particular instant .