Much has been written about mysticism in Forster's novels, primarily in A Passage to India. It is not, however, mysticism per se with which Forster is here concerned, but rather the mysticism of Hinduism. Any understanding of the mystic element in this novel requires some knowledge of the religion on the part of the reader. (See the short paragraph at the beginning of the commentary on Part III, the "Temple" section.)
But even such knowledge will not bring complete or immediate understanding, for Forster is not attempting to explain Hinduism, or to proselytize for it; his method of dealing with it is, in the main, allusive rather than expository.
The novel is full of unanswered questions: "Mrs. Moore felt increasingly (vision or nightmare?) that, though people are important, the relations between them are not." "God si love. Is this the first message of India?" The reader can find many others for himself; since Forster himself does not pretend to answer them, it would be presumptuous to do so here. In fact, part of the essence of mysticism is its inexpressibility; it cannot be reduced to words, to questions with answers.
However, the reader should at least be aware of those elements that have mystical overtones — primarily the character of Mrs. Moore, the echo and its effect on her, and many of the aspects of Hinduism.