A long bad day begins when after Mitch rescues a struggling swimmer, the local Disease Control Center places the entire Baywatch Headquarters under quarantine after the swimmer shows symptoms of a deadly virus.

Mitch rescues a troubled young woman, named Sara, from her boat after it catches afire after which she charms Mitch and gets his mother, Irene, to hire her as a nanny for Neely's baby, Ashley. But Mitch gets concerned when Sara quickly develops a dangerous obsession with him and tries to win his affections at any cost. When Mitch lets Sara down, she immediately shows her true colours and plots to make Mitch's life a nightmare.