Oppenheimer completes his PhD and meets scientist Isidor Isaac Rabi. They later meet theoretical physicist Werner Heisenberg in Switzerland. Wanting to expand quantum physics research in the US, Oppenheimer teaches at the University of California, Berkeley and the California Institute of Technology. He marries Katherine "Kitty" Puening, a biologist and ex- communist, and has an intermittent affair with Jean Tatlock, a troubled communist psychiatrist who later dies in an apparent suicide.