Keith was coming off a romance with model Niki Taylor.
Other spoilers may discuss the resurgence of Viki's alter ego Niki or speculate that Viki's behavior may indicate that Niki is indeed out of the box.
Over the years there have been many incarnations of Viki's alter egos, the most prominent of which is Niki Smith.
Niki was bad in all the ways that Viki was kind and good.
The show also deals with mental illness and how it affects not only the individual, as in the case of Viki and her alter ego Niki, but also the heritability of the problems.