With the show's popularity soaring in the fourth season (now the third most watched program of 1983-1984), former President Gerald Ford guest-starred as himself in 1983, along with his wife Betty and former Secretary of State Henry Kissinger. New characters included the charming and ambitious Farnsworth "Dex" Dexter (Michael Nader), the scheming Public Relations assistant Tracy Kendall (Deborah Adair), the unscrupulous playboy Peter de Vilbis (Helmut Berger), and Blake's illegitimate African American half-sister, Dominique Deveraux (Diahann Carroll). The main storylines included a custody battle between Steven and Blake over Steven and Sammy Jo's son Danny, and a false accusation of illegal weapons dealings orchestrated by Alexis to ruin Blake's financial empire. In the season finale, Fallon disappears just before her second wedding to Jeff (now divorced of Kirby) as her car seemingly collides with a truck on a stormy night (to accommodate the departure of Pamela Sue Martin from the series), while Alexis is arrested for the murder of Mark Jennings.