The source novel, Charles Williams' "Dead Calm", was partially inspired by the real-life murders of a family on-board a sailing ketch off the coast of Florida in 1961. The case involved a decorated WWII vet named Julian Harvey who was hired by the Duperrault family to skipper a boat ride from Fort Lauderdale to the Bahamas. Also on the boat was Harvey's wife. Upon returning from the Bahamas on Nov 12, 1961, Harvey murdered his wife (hoping to collect an insurance policy) and four members of the Duperrault family (Patriarch Arthur, his wife Jean, their 14 year-old son Brian, and 7 year-old daughter Renee). Another daughter, 11 year-old Terry Jo, had been asleep below-deck but by the time she responded to the screams above-deck Harvey had slaughtered her entire family and scuttled the boat so it would sink. Harvey then hopped in a dinghy and deserted Terry Jo, assuming she would drown. However, Terry Jo was able to use a corkboard as a flotation device as the ketch sank. She was able to survive in the Atlantic ocean for four days without food or water before being rescued by a Greek freight ship. Meanwhile, Harvey was rescued by the Coast Guard and upon returning to Florida spun a tale of the ketch being damaged by a squall and sinking with him being the lone survivor. Harvey was later informed that Terry Jo Duperrault was found alive and being brought back to Florida. Upon hearing this news, Harvey checked into a Miami motel and committed suicide. Terry Jo was able to make a full recovery.
