What are the motifs in A Passage to India by E. M. Forster?

The echo begins at the Marabar Caves is something that haunts Mrs. Moore and Adela for weeks after their visit. The disembodied sound makes them question both their identity and their place in India. The Marabar Caves is a place that separates them from the status quo of colonialism in India. The echo reminds them that they are both free and lost when removed from the rigid social structure of Colonial India.