Shot in that most forlorn of formats , widescreen black-and-white , the film stars Milland as a head of household who leaves on a camping vacation with his family -- his wife -LRB- Jean Hagen -RRB- , son -LRB- Frankie Avalon -RRB- and daughter -LRB- Mary Mitchel -RRB- -- just in time to escape the nuclear devastation of Los Angeles .