Jean and Paul are identical twins. Outsiders, even their parents, cannot tell them apart, and call them Jean-Paul. The mysterious bond between them excludes all others; they speak their own language; they are one perfectly harmonious unit; they are, in all innocence, lovers.

For Paul, this unity is paradise, but as they grow up Jean rebels against it. He takes a mistress and deserts his brother, but Paul sets out to follow him in a pilgrimage that leads all around the world, through places that reflect their separation--the mirrored halls of Venice, the Zen gardens of Japan, the...