What is the main conflict in Brazzaville Beach: A Novel by William Boyd?

As a young graduate student, Hope becomes infatuated with a newly-arrived mathematician, John Clearwater. She pursues him ardently and they marry quite quickly. Hope finishes her doctorate and takes a part-time position chronicling the plant life on an old estate near London. John immerses himself in his work, gradually becoming less and less rational, as is often the tragic case with genius.