Graves plays Steven Anders, a man on a mountain camping trip with his family. His wife, played by character actor Jay MacIntosh, needs to return home early, leaving him with his teen children David and Deborah, played by George O'Hanlon jr. (most recently seen in LOST) and Kathleen Quinlan (in everything from Ironside to CSI), respectively. While exploring a cave, mysterious waves of light (ostensibly freakish solar flares) flashed across the California sky. The three come out of the mountain to a changed world. As the mother had taken the vehicle, they are forced to hike home to Malibu, on a quest to reunite with her.
This is a fantastic picture. It sits in a special category of mine, with other such post-apocalyptic gems as the stark Ray Milland doomsday film PANIC IN THE YEAR ZERO, and well-known classics like THE OMEGA MAN and THE PLANET OF THE APES. Peter Graves is a surprisingly strong figure here (much as Milland was in the aforementioned), and the kids were both very good. Verna Bloom is captivating as a distraught mother. It's an unusual plot for television, and I think they pull it off memorably.
It's on Youtube for those that wish to see it; I'd love to see a DVD release.