She was caught between two allegiances, different, yet the same. Herself. Her race. Race! The thing that bound and suffocated her. Whatever steps she took, or if she took none at all, something would be crushed. A person or the race. Clare, herself, or the race. Or, it might be, all three. Nothing, she imagined, was ever more completely sardonic. 
 Passing, in my reading, is a book on identity. First those identities which are public, which we perform and act out. Then those identities which we ignore, or deny, or those selves which we don't even know we have. 
 The story is set in 1920s New York, with two light-skinned black women - Irene Redfield, and Clare Kendry. Clare, to Irene's astonishment, 'passes' or pretends to be white, with all the legal rights and social privileges which entail. The rest of the book follows Irene as she enters this world, and follows her own questioning her identity. The emotional toil of living a lie for so long. 
 The writing of the book is understated, yet it conceals a great emotional depth, as Irene and Clare conceal their own emotions. The events of the book's climax (the window scene) show both the terrible force and ambiguity of these conflicts.